A bleed valve (30) for a gas turbine engine (10) comprises a diffuser (50), through which heated compressor bleed air flows (54) into a bypass duct (22) air stream (B), has a plurality of small holes (40). The plurality of holes (40) is divided into two or more arrays of holes (52p,q,r), each array of holes (52p,q,r) is angled (δ) away from one another so that their respective bleed flows (54p,q,r) do not coalesce. This separation improves mixing with the air stream (B) and helps prevent hot bleed air damaging nacelle and other engine components.