Passengers on a packed London train have been stunned when their evening commute was interrupted by a musical marriage proposal.

Adam King enlisted the help of his choir, the Adam Street Singers, to serenade his girlfriend, Lucy Rogers, with a rendition of Bill Withers' Lovely Day.

The 34-year-old tailor then asked Miss Rogers, 25, to marry him.

A YouTube video of the proposal, which has now gone viral, shows the groom-to-be getting down on one knee on board the 19.57 London Overground service to Watford Junction, before Miss Rogers bursts into tears and says yes.

Mr King told the Evening Standard: "I knew I wanted to do some kind of flashmob, but wanted it to be quite intimate - so I came up with the idea of the Overground train from Euston, where we live.

"The biggest problem was making sure Lucy made the train. There was only a three-minute window to get the choir, me and Lucy on.

"A lot of the choir are our friends, which made things even harder - we had to make sure she didn't recognise people."

Neil Robinson, director of the Adam Street Singers and part of the choir, spoke of his joy at how well the flashmob proposal had gone.

"For the last couple of months Adam and I have been planning the proposal together and we all got together on Monday this week to rehearse the song. It was quite a military operation.

"It couldn't have gone any better. We were worried about the train being delayed but nothing went wrong at all. Obviously the choir is extremely happy for them."