Knight was born in Stafford as John Knight Prescott, the son of Edward Knight Prescott, an actor, and Sarah Clews, a local wine merchant's daughter. He began his working life as a junior clerk in the office of a West India wine merchant in London. When his employer became bankrupt Knight turned to art. His father sent him for six months to Henry Sass to correct his drawing, and for a further six months to George Clint to improve his colouring. He became a student at the Royal Academy in 1823, later becoming a Royal Academician in 1844. He died in London in 1881 after a long illness. Knight was well known as a painter of portraits and genre scenes, and is the only Stafford-born artist with a national reputation.