The singer, who is married to actress Gwyneth Paltrow, announced his feelings after making an unexpected appearance at Mencap's Little Noise charity concert, at London's Union Chapel, on Monday night (27.11.06).
Martin played a short acoustic set which included new Coldplay song "Buckets of Rain" and cover versions of The Killers' recent hit "When You Were Young" and Bob Dylan's "Buckets of Rain," which he dedicated to Lily.
He said: "This is for Lily Allen. She's gorgeous, she's sweet. And if I wasn't married."
Allen later took to the stage herself and during her set performed a cover of The Kooks song "Na?ve."