An American millionnaire placed envelopes full of cash all over a park and sent clues to their location out via the social networking site.
People were told to look for a "large space where green meets blue. Saturday neither early nor late" that shares a name with a place in California. Those who couldn't work it out from that were told to think about where Peter Pan might go for a swim.
Apparently, that was still not enough of a clue for some, so Jason Buzi – who has been revealed as the millionaire founder of the Hidden Cash project – finally gave the game away, tweeting: "Apparently hardly anyone looking in the right place. Kensington gardens near pond and Peter Pan! There you go! Now get some dough!"
That prompted crowds of people to turn up to the central London park. Some picked up sticks to poke around in the long grass, while other searched in the boughs of trees.
Those who found cash were encouraged to tweet pictures of themselves. One winner Adam Mills tweeted two pictures of himself with envelopes and promised to give the second to charity.
There was a friendly, collaborative atmosphere among the treasure hunters, said Joanna Burke, from London. She said she had already spoken to some of those who had found envelopes and picked up some tips. But she admitted she was still thinking taciaclly and didn't want to give away all of herbest insights.
"Come over here," she said, looking over her shoulder and walking a few paces away from other participants. "I bumped into someone who had just found £40 in a hole in a tree and then a girl at the same time within 20 minutes also found money in a tree," she said.
Burke said she had also been told that some of the envelopes were hidden in the long grass, so she said she planned to concentrate her efforts on that. She said that, like at least one lucky treasure hunter, she intended to give any winnings to charity.
Some, however, were a little more single minded. Friends Paul Wheeler and Paul Kettle, from Northern Ireland, both said they were most likely to go to the pub if they found some money. They said they had been searching in frustration, however. They insisted they had worked it out from the clues tweeted from the @HiddenCash account, but that it had then been made "too easy", so a lot more people than they had expected turned up.
Frenchman Fabrice Léo, on the other hand, thought he might get a good meal in a restaurant. "If I find a lot, perhaps I will give some away," he added.
The treasure hunt was set up by 43-year-old US property investor Jason Buzi, who hid tens of thousands of dollars in America and tweeted clues to help people find the money. The treasure hunts took place in Los Angeles, New York, Chicago and Houston. He hid 20 envelopes in London and is reportedly considering similar hunts in the rest of the UK, as well as Paris and Madrid.
In an interview with the Daily Telegraph, he said: "We want to see how London goes first and then we'll decide whether to expand it around the UK. Londoners are big Twitter users so I'm sure there will be quite a crowd. You guys seem to love a treasure hunt so it could become a scramble for the money."
guardian.co.uk © Guardian News and Media Limited 2010