It was held up last month and will be on the last Friday of every month, according to Critical Mass, a movement of cycling campaigners and environmentalists. Similar rides took place in a dozen cities including Manchester, Cardiff and Glasgow. More are expected next month.
Critical Mass campaigns for better facilities for cyclists, fewer cars and less pollution.
Patrick Field, a self-confessed cycling fanatic, said: "By the middle of the summer I wouldn't be surprised to see the numbers in four figures. We are saying `we are having a good time, what's your problem?' "