Reuters) - A London law firm confirmed the worst-kept secret in show business on Monday by sending congratulations to one of its lawyers and Hollywood leading man George Clooney on their engagement. Media speculation that Clooney had gone back on his vow never to remarry grew at the weekend after his girlfriend, human rights lawyer Amal Alamuddin, was spotted wearing a large ring on her wedding finger at a Los Angeles restaurant. The couple have said nothing and Clooney's representative declined to comment on the actor's personal life, but on Monday Alamuddin's law firm released a statement. "The barristers and staff of Doughty Street Chambers offer their best wishes and congratulations to Ms Amal Alamuddin, a member of Chambers, and Mr George Clooney on their engagement to be married," the firm said. Clooney, 52, and Alamuddin, 36, have been dating since last October, according to media reports.