Although native to the province of Atholl in Perthshire, Steuart spent most of his adult life in London, before moving to the Isle of Man in his final years.

His work exhibited a "markedly neo-classical taste", with a fondness for tall, thin columns, narrow windows, and "a uniform severity of wall surface" which "verges on bleakness".

His surviving correspondence with the dukes amounts to about a hundred letters, in which Steuart not only discussed professional matters, but also passed on news and gossip from the English capital.

The client-patron relationship has been described as exceptional for the time, with Steuart rendering the Atholls many non-architectural services in London, such as negotiating business deals and even consulting medical professionals on their behalf.

In return, the dukes employed Steuart on a variety of projects, and wrote letters of recommendation to their peers which enabled him to mix with high society.