Britain's Prince Andrew sang happy birthday to Princess Eugenie using his iPad.

Prince Andrew

Prince Andrew

The royal marked his daughter's 25th birthday by pulling out a tablet device during the middle of a Palace function to ring Eugenie in New York and sang in unison with his 400-strong audience in the State Apartments at St James's Palace.

Talking to his audience, the prince 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."

The faces of the princess, as well as her sister, Princess Beatrice, and mother, Sarah, Duchess of York, smiled and waved back at the crowd.

He told her: "You will notice that we have somebody here to play (gesturing to the trumpeter)."

Then, he turned to the lance corporal and said: "If you will lead us in Happy Birthday please..."

Eugenie thanked her father for the gesture, but the Duchess of York was less forthcoming with praise.

She joked: "We think you all need to go for choir practice."

However, the prince was happy with his efforts, saying: "Having been told this was a bad idea, it worked."