X0303 4 2010-11-18 0001141719 ALTERRA CAPITAL HOLDINGS Ltd ALTE 0001389155 Roberts Joseph William C/O ALTERRA CAPITAL HOLDINGS LIMITED ALTERRA HOUSE, 2 FRONT STREET HAMILTON, BERMUDA D0 HM 11 BERMUDA 0 1 0 0 EVP & CFO Common Shares 2010-11-18 4 S 0 30000 20.15 D 137998 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $20.00 to $20.36, inclusive. The reporting person undertakes to provide to Alterra Capital Holdings Limited, any security holder of Alterra Capital Holdings Limited, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnote (1) to this Form 4. Bernard K. Asirifi, Attorney-in-Fact 2010-11-22