Johnny Dewe Mathews was born in London and educated at Ampleforth College near York. He trained and qualified as an architect in 1970 at the Central London Polytechnic. He then travelled in the US and Central America, designing houses in Mexico for archaeological workers who were on long-term excavation projects of ancient Zapotec temples.
Just before he returned to England, Mathews went to an exhibition of self-portrait photographs by the artist Lucas Sumares and was instantly inspired to take up photography. He returned to London in 1972 and started taking photos of artists, fashion designers and rock stars. After only 2 years of taking photos the artist Patrick Proctor introduced him to Sir Roy Strong, the then director of the National Portrait Gallery. He and Colin Ford (in charge of photography) offered Mathews a one-man show, and in 1974, he exhibited his photos at the National Portrait Gallery.
Mathews recalls the first ever photo shoot with Queen at his studio in Primrose Hill in September 1974, "They were very confused by my casual approach to taking photos. I had no assistants and no lights and only listened to blues music. Freddie warmed up when I told him that I had taken many photos of Derek Jarman and Andrew Logans Alternative Miss World; I also told him about photographing Andy Warhol at his Mao show in Paris with a Brownie Box camera. He looked at me as if he was genuinely impressed!"