Is it me or is the decision by director Stephen Daldry to cast Kristin Scott Thomas as the Queen in this revival of Peter Morgan's play an odd one? Facially, they couldn't be more different. Yet Scott Thomas makes up for being more beautiful than our monarch with a panoply of mannerisms and gestures that are spot-on.

Among these are the way the Queen stands with feet planted flatly and the unique version of posh with which speaks. I had my doubts about Morgan's play when it was first seen a couple of years ago with the Queen played by Helen Mirren. Based on the weekly meetings Elizabeth II has with her Prime Ministers - starting with Churchill, there have been 12 of them since she was crowned in 1953 - the play then came across as more royalist propaganda than a searching drama.

But now it has been somewhat spiced up with some proper politics. This time, Blair makes an appearance putting the case for military action in Iraq, a moment that is seen here as a folly that uncannily mirrors Eden's Suez policy. The smooth but shallow Cameron, meanwhile, is shown preparing for an election, although nothing passes between them on how the UK was nearly broken up during his watch, which one imagines would have made for an interesting chat.

All these private encounters - including a gauche but irreverent Harold Wilson - are guesswork of course. But Morgan's guesses feel thoroughly well researched. The play's potency lies in a portrait of a queen who, whatever one's views on the existence of a royal family in a modern democracy, who comes across as extremely likeable.