UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.                )

Filed by the Registrant   ☒             Filed by a Party other than the Registrant   ☐

Check the appropriate box:

Willis Towers Watson Public Limited Company

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check the appropriate box):

On July 16, 2020, in accordance with Rule 15 of the Irish Takeover Panel Act, 1997, Takeover Rules 2013, Willis Towers Watson public limited company (“WTW”) and Aon plc sent the following communication to WTW equity award holders.

If you are in any doubt about the action you should take, you are recommended to immediately seek your own personal financial advice from one or more of your stockbroker, bank manager, solicitor, accountant, or an independent professional financial adviser who, if you are resident or taking advice in Ireland, is duly authorised under the European Union (Markets in Financial Instruments) Regulations 2017 (as amended) or the Investment Intermediaries Act 1995 (as amended), or, if you are not so resident and are not taking advice in Ireland, another appropriately authorised independent professional adviser.

Unless otherwise defined herein, the capitalized terms used in this letter shall have the meanings ascribed to those terms in the joint proxy statement (and/or the Business Combination Agreement attached thereto) circulated to WTW shareholders on or about 8 July 2020.

EXPLANATION FOR WTW EQUITY AWARD HOLDERS

under the

WILLIS TOWERS WATSON EQUITY PLANS

in connection with the

BUSINESS COMBINATION OF

WILLIS TOWERS WATSON PUBLIC LIMITED COMPANY

AND

AON PLC

The opinion of Goldman Sachs & Co. LLC (“Goldman Sachs”) which is annexed to the joint proxy statement prepared by Aon plc (“Aon”) and Willis Towers Watson Public Limited Company (“WTW”) containing important information about the Proposed Combination (as defined herein) does not constitute a recommendation as to how WTW equity award holders may decide to act with respect to the WTW Options, WTW Share Awards and/or WTW Phantom Stock Unit Awards (each as defined herein) held by them nor does it express an opinion as to what the value of Aon shares will be when issued or the price at which Aon shares will trade at any time.

The directors of Aon accept responsibility for the information contained in this letter relating to Aon and the directors of Aon and members of their immediate families, related trusts and persons connected with them. To the best of the knowledge and belief of the directors of Aon (who have taken all reasonable care to ensure that such is the case), the information contained in this letter for which they accept responsibility is in accordance with the facts and does not omit anything likely to affect the import of such information.

The directors of WTW accept responsibility for the information contained in this letter relating to WTW and the directors of WTW and members of their immediate families, related trusts and persons connected with them. To the best of the knowledge and belief of the directors of WTW (who have taken all reasonable care to ensure such is the case), the information contained in this letter for which they respectively accept responsibility is in accordance with the facts and does not omit anything likely to affect the import of such information.

The release, publication or distribution of this letter in or into certain jurisdictions may be restricted by the laws of those jurisdictions. Accordingly, copies of this letter and all other documents relating to the Proposed Combination are not being, and must not be, released, published, mailed or otherwise forwarded, distributed or sent in, into or from any such restricted jurisdictions. Persons receiving such documents (including, without limitation, nominees, trustees and custodians) should observe these restrictions. Failure to do so may constitute a violation of the securities laws of any such jurisdiction. To the fullest extent permitted by applicable law, Aon and WTW disclaim any responsibility or liability for the violations of any such restrictions by any person.

Goldman Sachs is acting as financial adviser to WTW and no one else in connection with the Proposed Combination and will not be responsible to anyone other than WTW for providing the protections afforded to clients of Goldman Sachs or for providing advice in relation to the Proposed Combination, the contents of this letter or any transaction or arrangement referred to herein. Goldman Sachs accepts no duty, liability or responsibility whatsoever (whether direct or indirect, whether in contract, in tort, under statute or otherwise) to any person who is not a client of Goldman Sachs in connection with this letter, any statement contained herein or otherwise.

IMPORTANT ADDITIONAL INFORMATION HAS BEEN AND WILL BE FILED WITH THE SEC.

In connection with the Proposed Combination, on 8 July 2020, WTW and Aon filed with the Securities and Exchange Commission (the “SEC”) a definitive joint proxy statement containing further information relating to the implementation of the Proposed Combination. BEFORE MAKING ANY VOTING DECISION, WTW’S SHAREHOLDERS ARE URGED TO READ THE INFORMATION CONTAINED AND INCORPORATED BY REFERENCE IN THE JOINT PROXY STATEMENT, AND THE OTHER RELEVANT DOCUMENTS FILED OR TO BE FILED WITH THE SEC IN CONNECTION WITH THE PROPOSED COMBINATION, CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED COMBINATION AND THE PARTIES TO THE PROPOSED COMBINATION. WTW’s shareholders and investors may obtain, without charge, a copy of the joint proxy statement and other relevant documents filed with the SEC from the SEC’s website at http://www.sec.gov/edgar.shtml or by requesting them in writing or by telephone from WTW at the following address, email or telephone number: Innisfree M&A Incorporated, c/o WTW Company Secretary, 501 Madison Avenue, 20th Floor, New York, New York 10022; (888) 750-5884; corporatesecretary@willistowerswatson.com; or Innisfree M&A Incorporated, c/o Matheson, 70 Sir John Rogerson’s Quay, Dublin 2, Ireland; +353 1 232 2000; dublin@matheson.com

NO OFFER OR SOLICITATION

This letter is for information purposes only and is not intended to and does not constitute, or form part of, an offer, invitation or the solicitation of an offer or invitation to purchase, otherwise acquire, subscribe for, sell or otherwise dispose of any securities, or the solicitation of any vote or approval in any jurisdiction, pursuant to the Proposed Combination or otherwise, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law.

In particular, this letter is not an offer of securities for sale into the United States. No offer of securities shall be made in the United States absent registration under the U.S. Securities Act of 1933, as amended (the “Securities Act”), or pursuant to an exemption from, or in a transaction not subject to, such registration requirements.

Any securities issued as a result of the Proposed Combination by means of a scheme of arrangement are anticipated to be issued in reliance upon the exemption from the registration requirements of the Securities Act pursuant to the exemption from registration set forth in Section 3(a)(10) thereof.

Subject to the right of Aon to implement the Proposed Combination by way of a Takeover Offer as an alternative to the scheme, and subject to the provisions of the Business Combination Agreement entered into between WTW and Aon and with the Irish Takeover Panel’s consent, the Proposed Combination will be implemented solely by means of the scheme documentation, which will contain the full terms and conditions of the Proposed Combination, including details of how WTW’s shareholders may vote in respect of the Proposed Combination.

PARTICIPANTS IN THE SOLICITATION

Aon, WTW and their respective directors and executive officers may be deemed to be participants in the solicitation of proxies from shareholders in proposed connection with the Proposed Combination. Information regarding the persons who may, under the rules of the SEC, be deemed to be participants in the solicitation of shareholders, including a description of their direct or indirect interests, by security holdings or otherwise, is set forth in the joint proxy statement. Additional information about Aon’s directors and executive officers is contained in Aon’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 14, 2020, and its Proxy Statement on Schedule 14A, dated and filed with the SEC on April 24, 2020. Additional information about WTW’s directors and executive officers is contained in WTW’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 26, 2020, and its Proxy Statement on Schedule 14A, dated and filed with the SEC on April 27, 2020.

FORWARD-LOOKING STATEMENTS

This letter contains certain statements that are forward-looking, as that term is defined in the Private Securities Litigation Reform Act of 1995. Forward-looking statements are prospective in nature and are not based on historical facts, but rather on current expectations of management about future events. Forward-looking statements can often, but not always, be identified by the use of words such as “plans,” “expects,” “is subject to,” “budget,” “scheduled,” “estimates,” “forecasts,” “potential,” “continue,” “intends,” “anticipates,” “believes,” or variations of such words, and statements that certain actions, events or results “may,” “could,” “should,” “would,” “might” or “will” be taken, occur or be achieved.

Although management believe that the expectations reflected in these forward-looking statements are reasonable, it can give no assurance that these expectations will prove to be correct. By their nature, forward- looking statements involve risks and uncertainties because they relate to events and depend on circumstances that will occur in the future. There are a number of factors that could cause actual results and developments to differ materially from those expressed or implied by the forward-looking statements. Such factors include, but are not limited to, the possibility that the Proposed Combination will not be consummated, failure to obtain necessary shareholder or regulatory approvals or to satisfy any of the other conditions to the Proposed Combination, adverse effects on the market price of Aon and/or WTW securities and on Aon and/or WTW’s operating results for any reason, including, without limitation, because of the failure to consummate the Proposed Combination, the failure to realize the expected benefits of the Proposed Combination (including anticipated revenue and growth synergies), the failure to effectively integrate the combined companies following consummation of the Proposed Combination, negative effects of an announcement of the Proposed Combination, changes in global, political, economic, business, competitive, market and regulatory forces, future exchange and interest rates, changes in tax laws, regulations, rates and policies, future business acquisitions or disposals, or any announcement relating to the proposed consummation of or failure to consummate the Proposed Combination on the market price of Aon and/or WTW securities, significant transaction and integration costs or difficulties in connection with the Proposed Combination and/or unknown or inestimable liabilities, pending or potential future litigation associated with the Proposed Combination, the potential impact of the announcement or consummation of the Proposed Combination on relationships, including with suppliers, customers, employees and regulators, and general economic, business and political conditions (including any epidemic, pandemic or disease outbreak) that affect the combined companies following the consummation of the Proposed Combination.

The factors identified above are not exhaustive. Aon, WTW and their subsidiaries operate in a dynamic business environment in which new risks may emerge frequently. Other unknown or unpredictable factors could also cause actual results and developments to differ materially from those expressed or implied by the forward-looking statements. Forward-looking statements should therefore be construed in the light of such factors. You are cautioned not to place undue reliance on any forward-looking statements, which speak only as of the date made.

Further information concerning Aon and its businesses, including economic, competitive, governmental, regulatory, technological and other factors that could materially affect Aon’s results of operations and financial condition, is contained in Aon’s filings with the SEC. See Aon’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 14, 2020, Aon’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020, filed with the SEC on May 1, 2020, and additional documents filed by Aon with the SEC, the contents of which are not incorporated by reference into, nor do they form part of this letter, for a further discussion of these and other risks and uncertainties applicable to Aon’s businesses.

Further information concerning WTW and its businesses, including economic, competitive, governmental, regulatory, technological and other factors that could materially affect WTW’s results of operations and financial condition, is contained in WTW’s filings with the SEC. See WTW’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 26, 2020, WTW’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2020, filed with the SEC on April 30, 2020, and additional documents filed by WTW with the SEC, the contents of which are not incorporated by reference into, nor do they form part of, this letter, for a further discussion of these and other risks and uncertainties applicable to WTW’s businesses.

Any forward-looking statements in this letter are based upon information available as of the date of this letter which, while believed to be true when made, may ultimately prove to be incorrect. Other than in accordance with legal or regulatory obligations, neither WTW nor Aon is under any obligation, and each expressly disclaims any intention or obligation, to update or revise any forward-looking statement, whether as a result of new information, future events or otherwise. All subsequent written and oral forward-looking statements attributable to Aon, WTW and/or any person acting on behalf of either of them are expressly qualified in their entirety by the foregoing paragraphs, and the information contained on any websites referenced in this letter is not incorporated by reference into this letter.

DEALING DISCLOSURE REQUIREMENTS

Under the provisions of Rule 8.3 of the Irish Takeover Panel Act, 1997, Takeover Rules, 2013 (the “Irish Takeover Rules”), if, during an “offer period,” any person is, or becomes “interested” (directly or indirectly) in 1 per cent. or more of any class of “relevant securities” of Aon or WTW, all “dealings” in any “relevant securities” of Aon or WTW (including by means of an option in respect of, or a derivative referenced to, any such relevant securities) must be publicly disclosed by no later than 3.30pm (Eastern time) in respect of the relevant securities of Aon and WTW on the business day following the date of the relevant transaction. The requirement will continue until this offer period ends. If two or more persons co-operate on the basis of any agreement, either express or tacit, either oral or written, to acquire an interest in relevant securities of Aon or WTW, they will be deemed to be a single person for the purposes of Rule 8.3 of the Irish Takeover Rules. Under Rule 8.1 of the Irish Takeover Rules, all dealings in relevant securities of WTW by Aon, or relevant securities of Aon by WTW, or by any party acting in concert with either of them must also be disclosed by no later than 12 noon (Eastern time) in respect of the relevant securities of Aon and WTW on the business day following the date of the relevant transaction. Interests in securities arise, in summary, when a person has a long economic exposure, whether conditional or absolute, to changes in the price of securities. In particular, a person will be treated as having an interest by virtue of the ownership or control of securities, or by virtue of any option in respect of, or derivative referenced to, securities.

Terms used in this paragraph should be read in light of the meanings given to those terms in the Irish Takeover Rules. If you are in any doubt as to whether or not you are required to disclose dealings under Rule 8 of the Irish Takeover Rules, consult with the Irish Takeover Panel’s website at www.irishtakeoverpanel.ie or contact the Irish Takeover Panel by telephone on +353 1 678 9020.

July 16, 2020

Dear WTW Equity Award Holder,

The directors of WTW, who have been so advised by Goldman Sachs, consider the treatment of the WTW Options, WTW Share Awards and WTW Phantom Stock Unit Awards described in this letter to be fair and reasonable. In providing financial advice to the directors of WTW, Goldman Sachs has taken account of the commercial assessments of the directors of WTW in relation to the Proposed Combination and the WTW Options, the WTW Share Awards and WTW Phantom Stock Unit Awards.

Yours faithfully,