He was, along with his partner Edward Joseph Hansom, among the foremost Catholic architects in North East England during the Victorian era.

It was here that Dunn met his future partner Edward Joseph Hansom, the son of his employer.

Across the valley from Prudhoe is Castle Hill House (1878–9), which he designed and built as his own home in Wylam.

Previously he had lived in Gateshead, where he was an Alderman, Mayor and a Justice of the Peace for County Durham.

[3] In 1901 the Dunns moved to Wood House, Branksome Park, in Bournemouth, where he died on 17 January 1917 aged 85.