A year ago, the 25-year-old was shelling prawns and waiting tables, earning minimum wage at a Japanese restaurant.
Today, he is travelling the world as a member of boyband Collabro, a quintet which found success as the winner of this year's reality television show Britain's Got Talent.
"I'm living the dream now, really. To be honest with you, the absolute biggest change in my life right now is not having to worry where the next rent is coming from.
I was scraping by," he tells Life! in a telephone interview from Hong Kong, one of the stops in his group's global promotional tour. Collabro, which impressed the show's judges and viewers with their impeccable voices and repertoire of musical theatre numbers, won this year's competition in June.
Simon Cowell, one of the judges, signed them on to his record label Syco and Stars, their debut album which was released in August, went to No. 1 on the British charts.
Many of the tracks from their debut album are tunes that they sang on the show, including Stars and Bring Him Home from Les Miserables.
It also includes their take on contemporary hits such as All Of Me by R&B/soul singer John Legend and Secrets by pop-rock outfit OneRepublic.
Redgrave cannot believe that the group's debut release kept popular singer-songwriter Ed Sheeran off the top spot.
He says: "It's insane, we all listen to his music and look up to him. We're not at the same level as Sheeran yet, but to be regarded alongside him is incredible."
Collabro met Sheeran for the first time when both acts performed recently at this year's Royal Variety Performance, an annual gala attended by the British royal family.
"We had a chat with him, but nothing was said about the album charts. He was very, very nice," he says with a laugh.
Redgrave, who had been part of a church choir from young and had occasionally taken part in amateur productions, joined the band after answering a call on social media.
None of the members were professional singers before they took part in Britain's Got Talent.
Michael Auger, 24, was a petrol garage sales assistant; Richard Hadfield, 21, a labourer; Jamie Lambert, 25, worked in a hospital; and Matthew Pagan, 21, was a kitchen salesman.
Lambert and Pagan, who were friends, came up with the idea for the group and recruited Auger, Hadfield and Redgrave via social media.
Just one month after they first got together in January this year, the five men joined the eighth season of Britain's Got Talent.
During the auditions, their powerful rendition of Les Miserables tune Stars impressed Cowell and the rest of the judges so much that they received a standing ovation from the panel and the audience.
Redgrave says that the band are on a mission to bring musical theatre to the forefront of popular culture and expose it to a new generation of fans.
He adds: "It's very niche at the moment. It's very big in London where West End is, but outside of London, it's not on the radar.
"I think musical theatre is a beautiful form of music. It's one of the few musical styles where you can get the story and the raw emotion in a song across to an audience."
This article was first published on November 26, 2014. Get a copy of The Straits Times or go to straitstimes.com for more stories.