Returning to Glasgow, c. 1875, he proved his skill in Classical design with Adelaide Place Baptist Church, Pitt Street (1875-7), Hillhead Baptist Church, Creswell Street (1883) and Wellington Church, University Avenue (1882-4).

He entered the City Chambers' competition of 1880, with a Gotho-Romanesque design inspired by Waterhouse's Manchester Town Hall (1867-77) and Natural History Museum, London (1873-81), but this was rejected for flouting the competition's 'Classic Only' rule.

Working almost exclusively in the more popular classical and renaissance styles for his commercial buildings, schools and houses, his designs include:

The Royal Clyde Yacht Club, Hunters Quay (1889-91); Woodcroft, Larbert (1890-1); Kelvingrove Art Gallery competition (1892, unbuilt); The South School, Paisley (1893-5); 59 Bath Street (1899-1900, dem. c. 1967); the Dr James Hederwick Monument, with a bronze portrait by J P Macgillivray , Glasgow Cathedral (1901); the Saracen Head tenement, Gallowgate (1906); and the interiors for the yachts, Mohican and Meteor, the latter for Kaiser Wilhelm II.

The Saracen Head Tenement, which replaced the historic Saracen Head Inn, was originally provided with a splendid, cast iron fountain in its back court designed and manufactured by Walter Macfarlane 's Saracen Foundry, which had occupied the site from 1850-62, before it relocated to Possilpark. The fountain, after years of neglect and ruin, and despite calls for its restoration as a potential tourist attraction, was destroyed in the 1950s (another historic landmark at the rear of the tenement was the ancient St Mungo's Well).

The Saracen Foundry also provided the ornamental railings and lamp standards for Watson's churches.

Watson used sculpture sparingly on his buildings, his most lavishly ornamented example being the former Evening Citizen Offices, 24 St Vincent Place, which includes carved lettering, arabesques, lion masks and grotesque animals and birds by James Hendry (1885-9).

Another example of his use of architectural sculpture is the former Adelphi Terrace Public School, 7 Florence Street (now Glasgow College of Building and Printing Annexe), which features tympana carved with Pharaonic and Elizabethan heads, together with scrolled acanthus ornament by an unidentified carver (1894).

His Garnetbank Primary School, 231 Renfrew Street, although a very plain building, does feature minor carver work on its Janitors house in the Art Nouveau idiom (1905).

In 1902, Watson restored one of the city's oldest commemorative monuments: the 17th Century, Scots Renaissance-style Thomas Hutcheson Monument, which stands beside the south west door of Glasgow Cathedral.

Dating from 1670 and originally built in sandstone, the restoration entailed the complete rebuilding of the monument in granite, and the replacing of some of its carved ornament, as confirmed by the discovery of its original, badly worn and discarded heraldic finial in the grounds of Barlanark House in the city's east end, in the 1930s, as well as incorporating the original Death's Head panel into its new framework, and the cutting of new dedicatory inscriptions. The carver responsible for the work was William Vickers .

Watson formed brief partnerships with Henry Mitchell and W J Millar, was elected FRIBA, 1884, and served as President of the GIA, 1895.

He was also a Governor of the Royal Technical College (now Strathclyde University) and designed their War Memorial (1920), his final work.

Watson died at his home, 11 Loudon Terrace, on 12 October 1920, and was buried in the Necropolis, his grave marked by an unusual cross of his own design.

Sources:

• The Bailie, vol. 47, no. 1216, 5 February, 1896
• Who's Who in Glasgow-1909, pp. 213-4
• GH [Obit], 14 October, 1920, p. 9
• RIBA Journal [Obit], vol. 28, 1920-28, pp. 20-78
• Gomme & Walker
• ML : Young Scrapbooks (Hutcheson Monument), Vol. 6, p. 66
• Prowler (Hutcheson Monument, Barlanark House), p 415 (ill.)