An exodus of landlords from prime London properties has helped boost sales supply, data suggests.

Knight Frank’s May indices for sales and lettings that look at high-end properties in the capital show that the number of £1m-plus listings in prime central London hit the highest level since October 2016 in May at around 8,000, while supply outside of the sector was at a four-year high of more than 7,000.

The agent attributed this to landlords selling up as a result of buy-to-let tax changes.

Knight Frank said landlords now account for 13% of buyers, down from 20% in May 2014 when the buy-to-let tax changes began.

The boost in supply meant average prices in prime central London were down 1.8% and fell 3.8% on the outskirts.

In prime lettings, the dip in supply meant annual rental growth turned positive in central London for the first time since January 2016 at 1.7%.

The ratio between the number of new prospective tenants and the number of new lettings listings also rose to 4.6 in May, which was the highest figure in more than ten years.