Amy Winehouse received a standing ovation after singing at a London awards show Tuesday night – her first performance since canceling
her recent tour dates.
"At the end of the performance, the room erupted in applause and wild cheering," Kevin Milburn, director of the Mercury Music Prize (which is awarded to the best British and Irish album of the past year), tells PEOPLE.
Amid allegations of drug and alcohol abuse
with husband Blake Fielder-Civil (whom she married in May
), Winehouse – citing exhaustion
– checked into a "retreat" in Essex, England last month and canceled several tour dates. She also withdrew from the Sept. 9 MTV awards
in order to "support her well-being."
There also was some question over whether she would make it to the Mercury Music Prize. But her father, Mitch, was all smiles after watching her belt out an acoustic rendition of "Love is a Losing Game" from her nominated album Back To Black
in what the BBC
described as her searing voice.
"She was very happy to be here. And I'm just thrilled she was here," said the elder Winehouse, according to the BBC. "She gave a brilliant performance and she looks well."
According to Milburn, "Amy had announced she would not be doing any performances for the next couple of months but flew in from her holiday in St. Lucia especially for the occasion."
Although she didn't win the Mercury Prize (which went to the new rave group, the Klaxons, for their debut album Myths of the Near Future
) Winehouse, 23, impressed the judges.
Conor McNicholas, a music-magazine editor on the panel, described her performance to the BBC as "amazing. ... I've never been to an awards ceremony where somebody has performed and the room has been genuinely silent, proper pin-drop stuff."
A spokesman for Island Records in the U.K. tells PEOPLE: "She was in really good form. She looked really well and sang fantastically well. It was great."