Terry Waite was kidnapped in Lebanon in 1987 while negotiating the release of western hostages as a special envoy of the Archbishop of Canterbury.
He was kept prisoner for almost five years.
Emmaus creates communities of homeless people in which everyone works together refurbishing and selling donated household goods. Waite visits these communities to raise their local profiles and acts as a spokesman for the charity.
"Those who have themselves experienced depression and isolation see in him a fellow survivor," says Madeline Reiss, media officer at Emmaus.
"The public view him as someone they can trust."
The charity values the time Waite spends with its beneficiaries behind closed doors. "Terry is happy to spend time talking to residents, staff and volunteers when there are no cameras or reporters there," says Reiss.
"He is not just a famous face, but someone with real insight."