From Longman Dictionary of Contemporary Englishbe a (dead) certbe a (dead) certCERTAINLY/DEFINITELY British English informal to be certain to happen or to succeed Put your money on Thorpe to win, he’s a dead cert. → cert
Examples from the Corpus
be a (dead) cert• One candidate, the outgoing Taoiseach and the then leader of Fine Gael, was a cert.• I knew my sons had been saying that of course Mum would cry - it was a dead cert!• No, this was a dead cert. 