John was educated at the Maidstone College of Art where he studied graphic design.
He worked from his studio in Croesgoch since 1967. He exhibited his paintings across Europe and also Africa and North America. Subsequently he worked in exhibition design and theatre design, but also began painting.
In 1965 he moved to Pembrokeshire, Wales.
Knapp-Fisher claimed he painted every day. "I tell students to do something every day – even if it’s a quick thumbnail sketch.
Rather like a dancer has to practise every day, a painter has to oil the hinges by doing little drawings." He preferred to paint from notes and drawings in his sketchbooks, rather than from photographs. As a result his favorite subjects were local to his studio, for example Porthgain Harbour.
Knapp-Fisher"s largest exhibition was in Johannesburg, South Africa, where he displayed over 60 paintings.
To mark his 80th birthday in August 2011, Knapp-Fisher was featured on the British Broadcasting Corporation Radio Wales Arts Show. He also held an exhibition of new paintings at the Martin Tinney Gallery in Cardiff. Knapp-Fisher once spent 5 years living on a boat in East Anglia.
He resided in Croesgoch with his partner, Gillian Pare.
Knapp-Fisher died at Withybush Hospital, Haverfordwest in February 2015 age 83.
In 1992 he was elected a member of the Royal Cambrian Academy of Artist