 Green began his mission in June 1968 , at the age of 53 , initially in <unk> on Saturdays , becoming a full @-@ time human billboard six months later on Oxford Street . He <unk> there from <unk> with a sandwich board attached to the bicycle , a journey of 12 miles ( 19 km ) that could take up to two hours , until he was given a bus pass when he turned 65 . 
