A wall structure for a wall bounding a combustion chamber of a gas turbine engine is disclosed having a first wall with an inner surface facing towards the interior of the combustion chamber and an outer surface facing away from the interior of the combustion chamber such that the inner surface forms a boundary of the combustion chamber and the outer surface has a surface roughness to prevent the formation of a fluid flow cooling layer which would cool the outer surface. The invention also has a second wall spaced from the outer surface of the first wall in a direction away from the interior of the combustion chamber so as to define a cooling fluid circulatory space between the first and second walls. A plurality of first perforations extend through the first wall in communication with the cooling fluid circulatory space to enable passage of cooling fluid from the space through the first perforations to form a cooling fluid film on the inner surface of the first wall.