Sam Smith will play the wedding singer in the 'Four Weddings and a Funeral' Red Nose Day sequel.
The 22-year-old singer/songwriter is set to play the role in the new mini-film 'One Red Nose Day and a Wedding' in which he will belt out a cover of Sir Elton John's version of 'Chapel of Love', as featured in the 1994 classic film.
A source told The Sun's Bizarre TV column: "They're chuffed to get Sam on board for this.
"He's always more than happy to do his bit for charity, and this is an iconic remake for a good cause. His cameo won't be massive, but viewers won't miss him.
"The team have kept his involvement under wraps, as although they're keen to build some hype around the release, they want a few surprises too."
It was previously revealed the wedding itself will feature Alicia Vikander and Lily James tying the knot.
The short features 'Tomb Raider' star Alicia playing Faith and 'Mamma Mia!' actress Lily portraying Miranda, the daughter of Hugh Grant's character Charles.
'Four Weddings and Funeral' - which is directed by Mike Newell and written by Richard Curtis - follows the adventure of Charles and his circle of friends as they each encounter romance.
The new film will pick up 25 years after the first movie - which ended with Charles jilting his first love Henrietta at the altar to start a relationship and have a young son with Carrie - and Richard has admitted that while the characters are older, they may not have learned from their previous mistakes.
He said: "We're all definitely older - I suspect no wiser. It's been really enjoyable working out what's happened to all the characters.
"And now they get back together for the 5th wedding. Where, as usual, not everything will go as planned."
Red Nose Day 2019 will air on March 15, 2019.