Hollywood star Michael Sheen has cleared debts of 900 people worth a total of £1m. The actor used £100,000 of his money to start debt acquisition company to help the people living in South Wales.

Four years ago Sheen, who was born in Newport, Wales, told his fans he was a “not-for-profit” actor. And he vowed to use the money he earns to help others.

The 56-year-old, known for roles in films such as Heartlands, Amadeus and Underworld, has now stepped in after the closure of Port Talbot’s last blast furnace, ending traditional steelmaking in south Wales. A new Channel 4 show called Michael Sheen’s Secret Million Pound Giveaway will tell the story next week, five months after the heartbreaking closure.

According to the BBC the show aims to show how some banks and finance companies profit from the most vulnerable people. The actor warned he did not have £100,000 to “throw around” so wanted to make sure the project would be “effective”.

He came to the decision to go ahead with the idea after meeting a woman in a Port Talbot cafe who told of “steelworkers in tears” as they lost their jobs. This is the latest of a series of projects by the Welsh actor.

Two months ago he said he was funding a new theatre company – the Welsh National Theatre. He also sold his houses to make sure the 2019 Homeless World Cup went ahead in Cardiff.

He appeared on the One Show to explain how the debt system works. He told how people’s debts get put into a bundle, with a debt-buying company then able to buy those bundles at a cut price.

While the money owed by people remains the same, the companies that own the debt can then sell them for less and less money. Sheen told how he used £100,000 of his own money to set up the debt acquisition firm which was able to buy £1m worth of debt because it had come down in value.

The company was not set up in Sheen’s name and he said he needed to be at “arm’s length from it”. He added he was unaware of the identity of people’s debts he paid off, just where they lived and what kind of debt it was.

Sheen added: “I would never know who they are. I still don’t know who they are.”

The hour-long documentary will air on Channel 4 on Monday, March 10 at 9pm.