A nickel-based alloy composition consisting, in weight percent, of: between 5.0% and 6.9% aluminium, between 0.0% and 11.0% cobalt, between 6.0% and 11.6% chromium, between 0.0% and 4.0% molybdenum, between 0.0% and 2.0% niobium, between 0.6 and 8.6% tantalum, between 0.0% and 3.0% titanium, between 8.4% and 15.2% tungsten, between 0.02 wt. % and 0.35 wt. % carbon, between 0.001 and 0.2 wt. % boron, between 0.001 wt. % and 0.5 wt. %. zirconium, between 0.0 and 0.5% silicon, between 0.0 and 0.1% yttrium, between 0.0 and 0.1% lanthanum, between 0.0 and 0.1% cerium, between 0.0 and 0.003% sulphur, between 0.0 and 0.25% manganese, between 0.0 and 0.5% copper, between 0.0 and 2.0% hafnium, between 0.0 and 1.0% vanadium, between 0.0 and 4.0% iron, between 0.0 and 1.0% rhenium, the balance being nickel and incidental impurities, wherein the following equations are satisfied in which WNb, WTa, WTi, WCr, WMo, WW and WRe are the weight percent of niobium, tantalum, titanium, chromium, molybdenum, tungsten and rhenium in the alloy respectively 6.6≤2WTi+WTa+1.44WNb, 22.2≥WW+WRe+1.16 WCr+1.7WMo, 13.9≤WMo+1.17(WW+3.3WRe).