An airfoil for a gas turbine comprising: an outer structure comprising a first wall; an inner structure comprising a second wall spaced relative to said first wall such that a cooling gap is defined between at least portions of said first and second walls (110, 210), an inner surface of said second wall defining an inner cavity, said inner structure further comprising a first separating member for separating said inner cavity of said inner structure into a cooling fluid supply cavity and a first cooling fluid collector cavity, said second wall comprising at least one first impingement passage, at least one second impingement passage, and at least one bleed passage; and a seal structure provided within said cooling gap between said first and second walls (110, 210) for separating said cooling gap into first and second cooling fluid impingement gaps (510, 520), said at least one first impingement passage extending from said cooling fluid supply cavity to said first cooling fluid impingement gap, said at least one bleed passage extending from said first cooling fluid impingement gap to said first cooling fluid collector cavity, and said at least one second impingement passage extending from said first cooling fluid collector cavity to said second cooling fluid impingement gap, said inner structure further comprising a second separating member such that said first and second separating members (220, 230) separate said inner cavity of said inner structure into said cooling fluid supply cavity, said first cooling fluid collector cavity and a second cooling fluid collector cavity, wherein said seal structure comprises first seal structure, said at least one bleed passage comprises at least one first bleed passage and said second wall of said inner structure further comprises at least one third impingement passage and at least one second bleed passage, wherein said seal structure further comprises a second seal structure within said cooling gap between said first and second walls (110, 210) such that said first and second seal structures (410, 420) separate said cooling gap into first, second and third cooling fluid impingement gaps (510, 520, 530), said at least one second bleed passage extends between said second cooling fluid impingement gap and said second cooling fluid collector cavity and said at least one third impingement passage extends from said second cooling fluid collector cavity to said third cooling fluid impingement gap. an outer structure comprising a first wall; an inner structure comprising a second wall spaced relative to said first wall such that a cooling gap is defined between at least portions of said first and second walls (110, 210), an inner surface of said second wall defining an inner cavity, said inner structure further comprising a first separating member for separating said inner cavity of said inner structure into a cooling fluid supply cavity and a first cooling fluid collector cavity, said second wall comprising at least one first impingement passage, at least one second impingement passage, and at least one bleed passage; and a seal structure provided within said cooling gap between said first and second walls (110, 210) for separating said cooling gap into first and second cooling fluid impingement gaps (510, 520), said at least one first impingement passage extending from said cooling fluid supply cavity to said first cooling fluid impingement gap, said at least one bleed passage extending from said first cooling fluid impingement gap to said first cooling fluid collector cavity, and said at least one second impingement passage extending from said first cooling fluid collector cavity to said second cooling fluid impingement gap, said inner structure further comprising a second separating member such that said first and second separating members (220, 230) separate said inner cavity of said inner structure into said cooling fluid supply cavity, said first cooling fluid collector cavity and a second cooling fluid collector cavity, wherein said seal structure comprises first seal structure, said at least one bleed passage comprises at least one first bleed passage and said second wall of said inner structure further comprises at least one third impingement passage and at least one second bleed passage, wherein said seal structure further comprises a second seal structure within said cooling gap between said first and second walls (110, 210) such that said first and second seal structures (410, 420) separate said cooling gap into first, second and third cooling fluid impingement gaps (510, 520, 530), said at least one second bleed passage extends between said second cooling fluid impingement gap and said second cooling fluid collector cavity and said at least one third impingement passage extends from said second cooling fluid collector cavity to said third cooling fluid impingement gap.