ADDITIONAL INFORMATION ABOUT THE PROPOSED MERGER AND WHERE TO FIND IT:This release relates to a proposed transaction between Alterra and Markel that will become the subject of a registration statement, which will include a joint proxy statement/prospectus, to be filed by Alterra and Markel with the SEC. This material is not a substitute for the joint proxy statement/prospectus that Alterra and Markel will file with the SEC or any other document that Alterra or Markel may file with the SEC or Alterra or Markel may send to its shareholders in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS AND ALL OTHER RELEVANT DOCUMENTS THAT MAY BE FILED WITH THE SEC OR SENT TO SHAREHOLDERS, INCLUDING THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS THAT WILL BE PART OF THE REGISTRATION STATEMENT ON FORM S-4, AS THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED MERGER. All documents, when filed, will be available free of charge at the SEC’s website ( www.sec.gov) or, in the case of Alterra, by directing a request to Joe Roberts, Chief Financial Officer, or Susan Spivak Bernstein, Senior Vice President, Investor Relations, at 441-295-8800 and, in the case of Markel, by directing a request to Bruce Kay, Investor Relations, at 804-747-0136]. PARTICIPANTS IN THE SOLICITATION: Alterra and Markel and their respective directors and executive officers may be deemed to be participants in any solicitation of proxies from both Alterra’s and Markel’s shareholders in favor of the proposed transaction. Information about Alterra’s directors and executive officers and their ownership in Alterra common stock is available in the proxy statement dated March 26, 2012 for Alterra’s 2012 annual general meeting of shareholders. Information about Markel’s directors and executive officers and their ownership of Markel common stock is available in the proxy statement dated March 16, 2012 for Markel’s 2012 annual general meeting of shareholders.