His paintings, illustrations and etchings, undertaken for himself and on behalf of many of the foremost architects of the Victorian period made him "the Piranesi of the Gothic Revival.

Commissions for government offices, town halls, churches for private benefactors, railway termini were all put out to tender and competing architects required draughtsmen to illustrate their plans.

"[1] In 1875, Haig made study trips to Italy and Sicily, which resulted in a multitude of drawings and watercolors of mainly medieval architecture.

Cardiff Castle, Knightshayes Court, the Church of Christ the Consoler at Skelton-on-Ure, St Mary's Church, Park House, the Speech Room, Harrow School, Castell Coch, Trinity College, Hartford, Connecticut and the designs for the re-decoration of Saint Paul's Cathedral:[5] as Burges designed his most important commissions, so Haig drew them.

"[1] Haig developed a second career as an etcher and his drawings and lithographs of European castles, palaces, landscapes and cathedrals became hugely popular in late-Victorian England.

[8] In a review of Haig's work published by the Royal Institute of British Architects in the year of his death, Maurice Adams wrote that "his architectural draughtsmanship ranks without a doubt amongst the foremost of his time and his graphic capability remains unique.