Tom Nairn, who has died at the age of 90, was a political philosopher and major figure in the new left politics of the 1960s.Subsequently, his advocacy of nationalism as a progressive force gave him guru status within the nationalist movement in his native Scotland.The journalist Neal Ascherson, his old friend, described Nairn's as the most forceful and original mind to confront, demask and anatomise the British state, not least by promoting awareness that Great Britain was a multinational state and not a united nation.