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When Michelle Obama put her arm round the Queen at Buckingham Palace, some of the more excitable elements of the media - particularly the Americans - suggested she may have been guilty of a breach of protocol.

They missed the real story, however. What was far more interesting was that the Queen put her arm round the First Lady.

It is less than 20 years ago that the Australian Prime Minister was branded “the Lizard of Oz” for committing the supposedly heinous crime of putting his hand on the Queen’s back during an official tour of Australia.

Now the Queen is not just putting up with physical gestures of affection from a woman she has only just met, but is reciprocating with one of her own.

The footage does not make it clear who made the first move. But given the Queen’s track record - she is not a woman known for doing warm, at least not in public - the fact that Mrs Obama is American, and that the President spent most of the first part of the day putting his arm round Gordon Brown, it can safely be assumed that it was the First Lady who took the initiative.

A breach of protocol? Hardly. Buckingham Palace was very relaxed today about the incident, and attitudes there have changed significantly since the days of Mr Keating and his lese-majesty. And no, they don’t issue instructions to people about not touching the Queen.

“This was a mutual and spontaneous display of affection and appreciation between The Queen and Michelle Obama,” said a Palace spokeswoman.

Almost from the moment they first met it was clear that the Queen and the Obamas were getting on well. They joked together, and by the time came to pose for photographs they were acting almost like old friends. Which, considering that they met for the first time that afternoon, was quick work.

So what does that mean for the future? Will every visiting head of state and their spouse feel free to hug the Queen whenever they feel like it?

That may be straining credibility somewhat. The Queen liked the Obamas, clearly, and she is past master at being nice to people the Foreign Office wants her to be nice to: a long line of American presidents would testify to that. But she is also expert at letting people know, in the subtlest but most unmistakable way, when they have overstepped the mark.

“She is a very warm person off duty,” said a Palace insider. “On duty, she has a very professional approach.”

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