Andrew Scott Robertson posted its highest sale total for more than two years at its latest auction, raising £21.4m.
Of the 73 lots offered, six were sold prior and 54 were sold on the day, for an 85% success rate.
A freehold four-storey house in Kensington, W1, arranged as four self-contained flats producing £10,759 pa, sold for £4.3m off a guide of £3.9m.
The private individual who bought it faced underbidding from a major property company, said auctioneer Robin Cripp.
“It was a crowded room and there seemed to be a very positive feel,” he said.
He added: “There had been concern that if Labour got in, there would be tinkering with rent control. Now there’s certainty and people just want to buy. Everyone is feeling a buzz.”
A four-storey property built by a philanthropist banker in 1866 also sold for more than its guide price of £1.4m.
The vacant building near Haywards Heath in West Sussex, is arranged as 29 self-contained flats on a 1.23-acre site. It sold for £1.9m.
The auction took place on 1 June at the Hotel Russell, WC1.
