The Duke of York has surprised a room full of business leaders by organising an impromptu Happy Birthday singalong for his daughter, Princess Eugenie.

Social media-savy Andrew on Monday used the camera on his tablet to contact his youngest daughter, who was celebrating her 25th birthday in New York with her sister, Princess Beatrice, and mother, Sarah Ferguson, all of whom appeared on screen to receive the greeting.

Accompanied by a trumpeter from the Scots Guards, Andrew led the 400-strong crowd at the PitchPalace entrepreneur awards in singing one verse of the song - emphasising his daughter's name in the third line for those who were unfamiliar with it.

Introducing the stunned audience to the singalong at St James's Palace, Andrew said: "We are going to do something new this evening.

"The lady in the middle is my youngest daughter and it's her 25th birthday today."

Addressing his daughter, who was wearing a pair of novelty glasses to mark the occasion, Andrew said: "You will notice that we have somebody here to play (the trumpeter)."

He then turned to the lance corporal and added: "If you will lead us in Happy Birthday please ..."

There were cheers from the crowd as the song came to an end, while plenty of others were waving and trying to capture the moment on their camera phones.

Eugenie said thank you and that she was "very proud, Pops" of her father's role in the awards, which celebrate innovation and technology in the creative industries.

But the singalong did not impress his ex-wife, who joked - in the style of a Eurovision announcement - that the rendition scored "zero points".