Irwin was primarily known as a landscape and figure painter. His permanent home was in Leamington Spa in 1940, but prior to that time he had studied at Academy Julian, Paris and at the Academie Beaux-Arts in Brussels. He was made a member of RBA in 1934, exhibiting regularly there, and also at the Royal Academy from 1936. His addresses were in London (1933), Ewell, Surrey (1935) and then in Warwickshire (1940). He was well regarded during his lifetime, but is now little known.

He suffered a bad spinal injury while serving with the South Lancashire Regiment on the outbreak of World War I and was taken prisoner until 1917. He endured great pain for the rest of his life.

His connection with Cornwall and STISA was in the final year of his life, though Whybrow had noticed his presence earlier in her 1921-1939 list of artists in and around St Ives. He painted a number of Cornish ports including Polperro. Irwin was well liked for his camaraderie, enthusiasm and cheerfulness and it was a great shock when in 1947 he took his own life.