Queen amused by Obamas' Invictus Games challenge

The Queen has dismissed an Invictus Games challenge from President Barack Obama and his wife Michelle - telling the world's most powerful man "Oh really, please".

Showing off her impeccable comic timing the monarch appears in the spoof video with her grandson Prince Harry to promote the five-day Games which will be launched in Orlando, Florida, on May 8.

As the royal pair sit discussing the Invictus Games the Queen's grandson gets a message on a smartphone from "FLOTUS" - First Lady of the United States - accompanied by a short burst of Hail To The Chief.

Harry tells the Queen "From Michelle, how very amusing, do you want to watch it together?" and he opens the video message when his grandmother says yes.

The Obamas are shown looking stern with their arms folded with some apparently uniformed servicemen and women behind them.

The First Lady says "Hey, Prince Harry, remember when you told us to bring it to the Invictus Games?"

"Careful what you wish for," adds the President as he points towards the viewer, and one of the servicemen says "boom" and opens his hand like an explosion.

The Queen and Harry look at each other smiling and the monarch says "Oh, really please", while Harry mockingly says "boom" with a smirk, and copies the hand gesture.

A link to the video was featured in an official Kensington Palace tweet which may have been posted by Harry as it was signed off with an "H" - "Unfortunately for you @FLOTUS and @POTUS I wasn't alone when you sent me that video - H."

The monarch famously appeared in a film sequence for the opening ceremony of the London Olympics alongside James Bond actor Daniel Craig and some of her corgis.

She is known for her sharp sense of humour which she uses to put nervous guests at ease, but Harry has said in the past he likes to think he is funnier than his grandmother.

He will be in Florida next month for the whole of the Invictus Games which will see more than 500 competitors from countries like Italy, Germany, Estonia, Jordan and the UK compete in 10 events - archery, indoor rowing, powerlifting, road cycling, sitting volleyball, swimming, athletics, wheelchair basketball, rugby and tennis.

Harry will be joined by the First Lady at the sporting spectacle for injured, wounded and sick servicemen and women and veterans, and in an interview said spectators would be taken on an "emotional rollercoaster".