When Sir John Soane – architect of the Bank of England and collector extraordinaire – died in 1837, he had something like 30,000 architectural drawings tucked into various albums and drawers inside his London home, now a house museum. In the intervening years, fewer than 200 have ever been out on display, so a new exhibition of them is significant, not least because they remain in terrific condition.

Soane, the son of a bricklayer who won the Royal Academy’s prestigious gold medal for architecture at 23, is a deeply fascinating character – one I like a little bit more each time I encounter him. In the current show, which extends over two sepulchrally lit rooms on the first floor, we learn that, during the Napoleonic wars (1803-1815) when the coffers of Soane’s by then widely renowned architectural practice ran frantically low, he refrained from laying off a single member of his staff. 

Not only that, but when he needed drawings for his lectures (he was elected the RA’s Professor of Architecture in 1806), he paid them from his own pocket. They turned out nearly a thousand of them, so the cost would have been substantial.

Some of these lecture drawings are on display here, including a play of fancy that overlays 10 buildings on top of one another in a series of coloured washes, to illustrate their prospective scales: so St Peter’s in Rome looms over, for instance, the Radcliffe Library in Oxford and the Rotunda at the Bank of England.

Soane was surveyor of the latter for 45 years, and in that time replaced almost every room – turn around and you’ll see a minutely detailed god’s eye drawing of the campus in its entirety. It’s attention to light and shadow is quite beautiful, stressing just how thin the boundary between architecture and sculpture really is.