A West End theatre audience were “stunned” last Monday evening when the Queen and Prince Philip discreetly joined them to watch the play War Horse.

As the lights dimmed for curtain-up, she and Prince Philip squeezed past audience members to get to their seats, apologising for the inconvenience, reports today's Evening Standard.

There was no visible entourage or security. In fact theatregoers claim it was an incredibly “ordinary” visit.

A journalist from The Lady magazine, who attended the performance, said: “The Queen and the Duke sat down as the lights dimmed and it was a huge shock when people realised who they were.

They were incredibly apologetic for asking people to let them past and there was no hubbub or fuss about it all

“They were incredibly apologetic for asking people to let them past and there was no hubbub or fuss about it all. It was amazing, they just sat among the audience and enjoyed the performance. At the interval they disappeared and reappeared very discreetly. When they left at the end, they were given a round of applause, which the Queen acknowledged with a wave.”

Those close to the Queen say she enjoys the theatre immensely and tries to make understated visits wherever possible, which “allows her to live a bit more of a normal life” says one aide.

She was last seen visiting the theatre in 2006 at the musical Billy Elliot, arriving in a green taxi at the Victoria Palace Theatre.