Middleton showed his first works with the
Ulster Academy of Arts in 1931, where he was to exhibit frequently until the late nineteen-forties. He first came to public attention with the inclusion of his works in the groundbreaking inaugural exhibition of the Ulster Unit at Locksley Hall, Belfast in December 1933. The Ulster Unit was a short-lived grouping of Ulster artists who took their inspiration from
Paul Nash's Unit One formed earlier in the same year. Just two years thereafter In the same year Middleton married Maye McLain, also an artist and a domestic science teacher, who was to die only four years later. Middleton was also a poet and writer, whom along with his wife, was an active member of the Northern Drama League in the 1930s, with whom he designed sets. After the death of his first wife he destroyed all of his early paintings and entered a period of seclusion at his Mother's home outside Belfast. Middleton became a follower of
Van Gogh and also of
James Ensor after viewing exhibitions in London and Belgium respectively. Throughout the thirties he was also a keen follower of Paul Nash,
Tristam Hillier and
Edward Wadsworth. After exposure to the works of
Salvador Dali, Middleton declared himself "the only surrealist painter working in Ireland". Middleton completed three paintings immediately after the
Belfast Blitz and the trauma of the events prevented him from working for six months Middleton's first solo exhibition was given by the
Belfast Municipal Gallery and Museum in 1943. It was the first exhibition staged at the Gallery when they re-opened after the
Belfast Blitz. At the time it was the largest one-person show the gallery had staged comprising one hundred fifteen works and it was also the first solo exhibition accorded to a local contemporary artist by the gallery. In an interview with Patrick Murphy in 1980, Middleton said that these paintings represented 'a first endeavour to harmonize the seemingly opposed and conflicting tendencies in human nature.' The Belfast exhibition was followed by his first one-man show at the
Grafton Gallery, Dublin in 1944. In the following year Middleton debuted at the
Irish Exhibition of Living Art where he was to return on a number of occasions, particularly in the periods 1949–55 and 1963–71. In 1945 Middleton was married for the second time, to Kate Giddens, In the same year Middleton returned to the Belfast Museum for a solo exhibition arranged by the Council for the Encouragement of Music and the Arts. Middleton's work was displayed in New York's
Associated American Artists Galleries in 1947 with a selection of works chosen by the Dublin art critic Theodore Goodman that included paintings by his Northern contemporaries
Dan O'Neill, George Campbell, Gerard Dillon and
Patrick Scott. Middleton also retired from the family business that year to devote his time to painting. He had worked at the business since his Father's death in 1933. Middleton then took his wife and child to live and work on
John Middleton Murry's Suffolk commune for a short period, before returning to Belfast in 1948. and
Sean O'Casey's Red Roses for Me in 1972, both at the latter. In 1952 Middleton exhibited alongside Daniel O'Neill, Nevill Johnson, Gerard Dillon and Thurloe Connolly at the Tooth Galleries in London. who presented a portrait of Middleton at the annual exhibition of the Royal Ulster Academy in 1965. A poet and musician, Middleton also produced murals, mosaics and posters. One such mural was commissioned for a house in Ballymena designed by the architect Noel Campbell in an international modernist style in 1951, and other works included a mosaic for a school in Lisburn, and a mural in a health clinic. Middleton was amongst the prizewinners at the
Arts Council of Northern Ireland's 4th Open Painting Exhibition in 1968. In the same year John Hewitt curated a joint exhibition of his paintings with TP Flanagan, at the
Herbert Art Gallery in Coventry. In 1972 Middleton toured extensively with his wife visiting Australia for two months and showing his works from the trip at the McClelland International Galleries on Belfast's Lisburn Road the following year. In 1973 he also visited Barcelona and later showed a series of surrealist works inspired by the two trips at the
Tom Caldwell Gallery in Belfast. Middleton lived for the last twelve years of life in
Bangor, County Down. == Death and legacy ==