Up to this point Sheen was probably best known for playing Tony Blair in The Deal and The Queen, though his cast of real-life people also includes Kenneth Williams, and he’ll soon be essaying Brian Clough. 
Incidentally, The Deal's implication that John Smith's chosen successor was Brown and Blair was a usurper put me in mind of how Lenin's will was ignored, but I doubt we'll be seeing Sheen play Stalin any time soon.In the meantime Sheen found that Frost and Blair share a strangely similar quality: the struggle between a steely will and a child-like desire to be liked.
That’s part of Frost/Nixon’s arc: the superficial playboy chat-show host faces a panward-heading career and possible bankruptcy as no-one wants the interviews that have swallowed a good chunk of his own and his friends’ money. But he pulls himself together and sits up all night doing the research to nail Tricky Dick, saving the day and forging himself a new reputation.
Similarly, Steve Bell famously skewered the young Blair as Bambi, whose radical agenda (if it was ever there) was immediately dropped for fear of scaring the voters. But a few years later the sight of a million people marching down Whitehall did nothing to change his mind. Steve Bell’s description of him as having one angry eye and one smiley one seems to sum that up.
For Blair/Sheen the decisive moment was the death of Princess Diana but for me – and I don’t think this was simply an inability by either Sheen or me to shake off the earlier role - in Frost/Nixon there were definitely some moments featuring a strange chimera: Blast or (more likely) Flair.
