[1] Middleton's prolific output in an eclectic variety of modernist styles is characterised by an intense inner vision, augmented by his lifelong interest in documenting the lives of ordinary people.

[14] 36 Arthur Street Belfast was the venue for a joint exhibition with the Czech artist Otakar Gregor, Joan Loewenthal and Sidney Smith in aid of the war effort at the end of 1940.

In part these women reflect his experience of Belfast and the difficult conditions that so many lived through.” This can be seen in the three female figures of The Poet’s Garden (1943), and even more so in The Conspirators (1942), both of which featured in the 1943 exhibition.

“The female form, pictorially and symbolically, becomes the landscape and the life force.” [17] The Belfast exhibition was followed by his first one-man show at the Grafton Gallery, Dublin in 1944.

[19] In 1945 Middleton was married for the second time, to Kate Giddens,[9] after both had been named co-respondents at the Belfast High Court a few months earlier, in civil servant Lionel P Barr's application for a decree-nisi.

[4] Middleton was a founding member of the Northern Ireland branch of the Artists International Association, who showed at the Belfast Municipal Gallery in spring 1945.

Other members included Joan Loewenthal, Kathleen Crozier, Pat Hicking, Trude Neu, Sidney Smith, Nevill Johnston, George Campbell and Gerard Dillon.

The Studio in review of that exhibition wrote that Middleton was:"without doubt one of the few Irish painters who can claim more than local significance...His pictorial language has a poetic richness of colour, plangent and melodious, composed in strength of tones that give depth and presence.

[25] In 1952 Middleton exhibited alongside Daniel O'Neill, Nevill Johnson, Gerard Dillon and Thurloe Connolly at the Tooth Galleries in London.

[9] Comprising almost three hundred exhibits, the show was accompanied by a monograph written by Middleton's lifelong friend, the patron and poet John Hewitt.

[29] The Royal Mail used Middleton's painting of Slieve na Brock in the Mourne Mountains to commemorate the Ulster '71 exhibition in a series of postage stamps that also featured the work of Tom Carr and TP Flanagan.

[31] 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.

[34] In the 1970s the Arts Council of Northern Ireland commissioned a documentary film portrait of Middleton entitled Trace of a Thorn, which was written and narrated by the Belfast poet Michael Longley.

"[36] This exhibition brought together 'works held in the public collection with those from private lenders [to provide a] full picture of this artist's talent and life.'

[9] In 1968, he was appointed MBE in the Queen's birthday honours list,[40] and in 1969 Middleton was elected an associate at the Royal Hibernian Academy with full membership conferred just a year later.

[9] The Arts Council of Northern Ireland granted Middleton a substantial subsistence award in 1970 which was to cover two years enabling him to retire from teaching to concentrate on painting full-time.