Princes William and Harry were kept "completely in the dark" by the Queen's transformation to Bond girl in the Olympic opening ceremony, they revealed.

The surprise scenes, shot in Buckingham Palace and featuring the Queen alongside Bond star Daniel Craig, proved to be some of the most memorable in the extravaganza last Friday.

And the Duke of Cambridge and brother Prince Harry revealed that not even they knew of their grandmother's film debut. Harry told the BBC's Sue Barker: "Both of us were slightly surprised with our grandmother's secret hobby that she had of parachuting which went down unbelievably well."

William said: "To be honest, we were kept completely in the dark about it, that's how big the secret was."

He said Harry had "got a sniff" of a rumour but they did not know for sure until they saw the scenes themselves.

"She did such a good performance that she has now been asked to star in the next Bond film," he joked.

"You don't expect the Queen to do something like that," Harry added, quipping: "What she does in her spare time is her spare time ..."

The brothers, along with the Duchess of Cambridge, have been spotted in crowds at various Olympic events since the start of the Games, rarely holding back in their cheering of Team GB.

William said seeing cousin Zara Phillips win a silver medal in the equestrian eventing was "absolutely fantastic", adding: "We both missed her European and World Championships when she was there, we were always supporting her from the television so to actually be there when she got a medal and they've done so well as a team, and to see Team GB do brilliant so early on in the Olympics, I had goose-bumps on the back of my neck and I got far too carried away."

Asked what their favourite Olympic moments were, William said Phillips' medal was the most emotional and most involved for him because of the personal connection. But he also paid tribute to the "unsung stars" who have had their "massive moment", such as Etienne Stott and Tim Baillie, who took gold in the canoe slalom.