Martyn was born in Harrow, North London, in 1959 and studied at Harrow School of Art (now the University of Westminster).

Martyn has always been interested in the human form and this has developed into an interest in form in general. He enjoys taking a central motif, be it a person, animal, still life or an element in a landscape and working it over and over again until the desired sensation is achieved. This process best lends itself to the media of oil paint and charcoal and is akin to that of a sculptor modelling in clay, adding and subtracting masses as required.

Portraiture is ideally suited to Martyn̛̛s approach and he was a prize-winner in the BP Portrait Awards at the National Portrait Gallery and was subsequently invited to produce a postcard for their "Mystery Postcards" exhibition 2006.

He was asked to take part in the first series of the BBC̛̛s "Star Portraits", where his portrait was the one selected by the sitter.

Martyn has exhibited several times at the Royal Academy Summer Exhibition and was awarded the Mike Harding Paint Award at the Discerning Eye Exhibition in 1996. He has exhibited at the Mall Galleries since 1993 with various societies such as the New English Art Club, Royal Society of Portrait Painters, Pastel Society and of course the RBA, being elected a member of the latter in 2006.