[1][2] From 1940 to 1945, he served with the New Zealand Expeditionary Force in North Africa and Italy as a truck driver, motorcycle rider, and machine gunner.

[7] Between 1953 and 1959, Allen was employed by the New Zealand Department of Education, first as a field officer to the Northern Māori Experimental Art Project, and then as a liaison organiser to secondary schools.

[3] In 1959, Allen collaborated with architect John Scott, designing the stained glass windows for Our Lady of Lourdes Church, Havelock North.

He also designed the "light modulators", made of rimu, glass and yellow perspex, that are installed above the entranceway to reduce afternoon sunlight entering the chapel.

[8] Auckland Art Gallery Toi o Tamaki curator Ron Brownson called Allen's 2.5-metre-high (8.2 ft) pan-cultural Christ one of the most significant wood carvings produced in New Zealand during that period.

[8] In 1962, Allen designed the concrete, stained glass and leaded light baldachin for St John's Church in Te Awamutu.