The spate of interest-rate rises has made many new buy-to-let purchases financially unviable, and will trigger an autumn slowdown in the rental market, warns Savills, the estate and lettings agency. It says that many landlords putting down minimal deposits won’t have mortgage cost covered by rents now that the base rate has hit 5.75% “Interests rate are now double non residential yields. This is a historically extreme position,” says Jacqui Daly, associate director of Savills’ research team.