A nickel based alloy composition including, by atomic per cent, between 12 and 15% of elements from the group of aluminium, titanium, tantalum and niobium, between 0.8 and 1.8% tungsten, between 5 and 8% aluminium, at least 28% of elements from the group of molybdenum, tungsten, chromium and cobalt, wherein the atomic ratio of the sum of titanium, tantalum and niobium to aluminium is between 0.6 and 1.1, and wherein the composition includes less than 1.5% molybdenum, the balance being nickel save for incidental impurities.