LONDON (AFP) - Britain's oldest worker has enjoyed a day off to celebrate his 100th birthday but explained he would become a "miserable sod" if he ever had to retire for good. "Buster" Martin, a mechanic for a south London plumbing firm who has 17 children and 70 grandchildren and great grandchildren, tried giving up work at the age of 97 but couldn't face the boredom. "Boredom is a big killer of men," he told the Daily Telegraph. "I went back to work because I like to keep active," adding that if he ever retired he would become "the most miserable sod you have come across." The centenarian, who grew up in an orphanage and first married when he was 14, joined the Grenadier Guards and served in World War II before switching to the Navy. In more recent years he worked on London market stalls. He now lives in south London, where one of his few concessions to modern technology is a television. "I have never in my life owned a phone -- they are a bloody nuisance," he said. "You can be sitting peacefully indoors and they start ringing. I hate them." Neither is he too keen on foreign holidays. "You are only going to spend a lot of money to go over and do the same things you would do here," he told the daily. "I am living a holiday here. I wake up every morning and am happy in what I do."