11/07/2011 05:29 pm ET Updated Jan 07, 2012

Flash Mob Marriage Proposal: British Proposal On The Train Goes Viral (VIDEO)

It was just a regular day for Lucy Rogers -- until she was serenaded on her way home from work and proposed to by her boyfriend on the 19.57 London Overground train to Watford Junction last Tuesday.

When a group of commuters on the train started singing Bill Withers' Lovely Day spontaneously, Rogers had no clue that anything was out of the ordinary. In fact, the 26-year-old assumed that the stunt was part of a flash mob. It wasn't until her boyfriend, Adam King, showed up on one knee that Rogers realized something was up.

It turns out that King had been planning the elaborate proposal since April, asking his choir mates from Adam Street Choir to help him surprise his girlfriend. The group had been rehearsing for months -- with King even building a replica of the carriage to make sure everything would go perfectly.

Even with careful planning, there were a few factors he couldn't control: "There was only a three-minute window to get the choir, me and Lucy on [the train]," King told British newspaper The Sun. And when Rogers decided to drive to work on the day of the proposal, King had to disconnect her car's battery to ensure that his girlfriend would take the train.

Rogers and King didn't expect their unique engagement story to become go public -- but it did. Viewed over 500,000 times on YouTube since Thursday, the flash mob marriage proposal video has become the latest viral sensation.

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