The Glaswegian William Dunn (1859-1934) and Edinburgh-born Robert Watson (1865-1916) met while working for James MacLaren in his London office in the late 1880s. William Dunn served his apprenticeship with Duncan MacNaughtan in Glasgow, and then moved to London to work in the office of Wallace and Flockhart where he would have encountered Thomas MacLaren and, through him, met his brother James MacLaren. Dunn and James MacLaren subsequently teamed up to enter competitions, their last being their successful entry for the Wembley Tower in 1890.

Robert Watson served his apprenticeship in Edinburgh with Robert Paterson, Hippolyte Blanc and Rowand Anderson. He arrived in London in 1887 intending to emigrate to Canada, began working for MacLaren, and then decided to cancel his travel plans and became MacLaren's partner. Surviving drawings and sketches reveal he worked on the High School of Stirling, 22 Avonmore Road in London and the Santa Catalina Hotel at Las Palmas. Both Dunn and Watson are likely to have worked on the Glenlyon estate buildings in Perthshire, the long running contract in MacLaren's office.

When James MacLaren died at the age of thirty seven in October 1890, Sir Donald Currie's patronage passed to Dunn and Watson who formed a partnership to continue the practice and provide a measure of financial support for MacLaren's widow and five young children. Robert Lorimer (1864-1929), who had worked part-time for MacLaren in the early months of 1890, joined the office for a year. The practice first supervised the completion of 10-12 Palace Court in Bayswater and the Fenchurch Street offices in the City. The practice became Dunn, Watson & Curtis Green in 1912 when William Curtis Green joined the partnership. Robert Watson died in February 1916; Dunn retired to Kenya in 1919 and died there on 7 February 1934: Dunn had South African connections through work for the Union Castle Line, and they had branch offices in Cape Town, Durban and East London. Green’s best known work is the façade for the Dorchester Hotel in London. In Fortingall he designed the Molteno Memorial Hall for Currie’s daughter. He died on 26 March 1960.

In Fortingall, Dunn and Watson completed MacLaren’s work on Kirkton Cottages, and reconstructed Fortingall Hotel from a sketch by MacLaren. They reconstructed Glenlyon House, probably from MacLaren’s ideas, and later added the laundry block. In 1894 they rebuilt the clachan of Ardtrasgairt, and in 1901 – 1902 the old kirk of Fortingall to which in 1913 they added a reredos and stone panels in memory of Sir Donald Currie. In 1913 they also built a new terrace of cottages in Fortingall. Nearby Fortingall they built Keltneyburn Reading Room and a new bridge over the Keltney Burn. Elsewhere in Perthshire, also for Currie, they refurbished Dunkeld Cathedral and built the Aberfeldy Cottage Hospital; and off the Isle of Skye built a house and cottages on Scalpay. In addition to much work in England and Africa, they built an iconic water tower in Romania.