Lucas was born in Leith. He was educated at George Heriot’s school, then worked for the Civil Service and studied law at Edinburgh University. He showed promise in drawing and painting at an early age, but his family discouraged him from considering art as a career. He attended life drawing evening classes at Edinburgh College of Art, but was otherwise self-taught. He exhibited regularly in Edinburgh from 1933 onwards. Towards the end of the 1930s, he switched from watercolour to oil painting and became interested in Surrealism. He held solo exhibitions at the New Gallery in Shandwick Place, Edinburgh, in 1950 and 1951. Following his marriage in 1952, he stopped painting, only resuming for a brief spell in the early 1980s.