Elvis Costello (born Declan Patrick MacManus 25 August 1954) is an English musician and singer-songwriter. Costello came to prominence as an early participant in London's pub rock scene in the mid-1970s, and later became associated with the punk rock and New Wave musical genres, before establishing his own unique voice in the 1980s. Steeped in wordplay, the vocabulary of Costello's lyrics is broader than that of most popular songs, and his music has drawn on dozens of genres.
There are many websites giving Elvis Costello as a 'famous vegetarian' but none with any evidence. This seems to have originated from the Vegetarian Society UK in 1990s, which they probably got from an interview somewhere. We await any further confirmation.