Born in Pontardawe, Wales, she grew up Welsh-speaking and began as a folk singer. She was "discovered" by Twiggy, and as a result became one of the first artists to record on The Beatles' "Apple" record label. Despite competition from a well-established star, Sandie Shaw, who recorded the same single at the same time, Mary had a number one hit with "Those Were the Days", and represented the United Kingdom in the 1970 Eurovision Song Contest with "Knock, Knock, Who's There?". After marrying record producer Tony Visconti, she withdrew from the pop music scene in order to have a family.