Veteran British broadcaster David Frost died of a heart attack on Saturday at the age of 74, media reports quoted his family as saying on Sunday. Frost, well-known for his 1977 interviews with former U.S. President Richard Nixon, died Saturday night on board the Queen Elizabeth cruise liner, where he was due to deliver a speech. \"My heart goes out to David Frost\'s family. He could be - and certainly was with me - both a friend and a fearsome interviewer,\" said Prime Minister David Cameron, who sent his condolences. A family funeral will be held soon, according to media reports.