The 57-year-old from Cowcaddens can easily relate to the men and women who will travel from across the globe to take part in the tournament, having found himself without a place to call home on several occasions in his adult life.
“These people are my peers, I can understand what they’ve been through,” he said. “The Homeless World Cup has the ability to transform people’s lives and I wanted to be part of it.
“Many of those playing will have reached rock bottom before - but playing at the tournament will see their confidence go through the roof.”
William admits he spent years in and out of prison as a result of long-standing issues with drugs and alcohol. But he’s now been sober for nine months and has found a flat of his own.
He is one of around 120 local volunteers who have experienced homelessness - but are now learning new skills by working at the Homeless World Cup, which kicks off in Glasgow’s George Square on Sunday, July 10.
The scheme, organised by Glasgow Life and Glasgow Sport, with support from the Big Lottery Fund, is one of several legacy projects associated with the event, which will see 512 players from 52 countries play a series of four-a-side games on three specially-constructed pitches in George Square.
“We’re providing a life-changing opportunity for an army of volunteers, many of whom have been affected by homelessness themselves, with a package of support and opportunities which will continue long after the last ball has been kicked,” said councillor Archie Graham, depute leader of Glasgow City Council.
“The Homeless World Cup not only shines an issue on the problem, but inspires people to do what they can to tackle it.”
The opening match of the week-long tournament will see the Scotland men’s team play Hong Kong on Sunday, with kick-off at 1pm. The Scots women’s side play Norway immediately afterwards, at 1.25pm.
All games, which last 20 minutes, are free to attend.
The Homeless World Cup was first staged in 2003 and was the brainchild of two street newspaper founders who were keen to create an event that could have a transformational effect on people’s lives.
Mel Young, a well-known social entrepreneur based in Edinburgh who founded the Scottish edition of The Big Issue, teamed up with Harald Schmied to organise the first tournament in Graz, Austria.
It has been staged every year since across four continents.
“The tournament’s success is beyond anything we could ever have imagined,” Young told The Scotsman.
“One of the key factors is football: it’s a very simple way of communicating a message. People understand it, even if they don’t like it. You don’t need to be very good at it to get involved.
“The atmosphere is infectious. The crowds are very supportive and it rubs off on the players - it’s their moment. They have often endured difficult circumstances, but now it’s their chance to shine.
“There’s a stereotypical view of a homeless person as someone sitting in the street with their hand out. But we change that perception - they’re now football stars playing in their national strip.”
The 61-year-old, who was appointed the new chairman of SportScotland in February, will step back from the day-to-day running of the tournament he helped create after next week’s event, but will remain on the board.
He is confident that Glasgow will prove to be the ideal host city. “It’s a very open, friendly city,” he said. “There is something about Glasgow - our values should resonate here.
“We’ve been so impressed with the local authorities and their experience of hosting big sporting events.”
Young insists you don’t need to be a keen football fan to enjoy the Homeless World Cup as a spectator.
“They are short games with fast, flowing football,” he said.
“There’s something about the atmosphere, and the connection with the players, that makes it very magnetic.
“I would say to people: if you have a spare hour in Glasgow, pop in, and you’ll probably find you really enjoy it.”