Most of us, we would like to think, would help out a relative, a friend and perhaps even a stranger in need. Maybe giving directions or lending a few quid. But how many of us would donate one of our organs to someone we will never meet?

That is exactly what Tom Cledwyn did in 2012. Since then, his life has been shaped by acts of generosity towards strangers, culminating in Drop Dead Generous, a social experiment giving 1,000 people $500 (£378) each to spend on helping others in creative ways. Backed by an anonymous philanthropist, the project is part grant scheme, part provocation: what happens if you trust people to be generous?

Cledwyn donated his kidney at 25, after reading about Kay Mason, the first person in the UK to give a kidney to a stranger.

“It was an honour to be able to do it. And the same applies to all forms of giving. It doesn’t have to be a kidney. It can be a smile, some time, or being there when someone is struggling,” he says. “The experience of giving is the closest thing I’ve experienced to something that really matters.

“I knew I’d get minimal feedback and would never meet the recipient. That felt important too, doing something without seeing the outcome.”

After the operation, he set up a blog called The Free Help Guy, trawling Gumtree and offering anonymous help to people who needed it, whether that meant moving house or fixing things around the home. Demand grew quickly, until the money ran out.

A stint at Meta followed, where he rose to become a senior executive, but after seven years he left, pulled back towards the idea that generosity could be scaled.

Together with co-founder John Sweeney, he launched Drop Dead Generous, with a $500,000 (£378,000) fund. At the time of writing, 266 grants have been awarded across 21 countries.

Applicants are asked two simple questions: who needs help, and what would you do with $500 to “blow their socks off”?