London’s best homes are proving a tough sell after the U.K. voted to leave the European Union.

The number of prime properties sold in London in the 12 working days after the referendum fell 43 percent from the same period a year earlier, according to data compiled by researcher Lonres. The number of homes under offer dropped 25 percent.

Home values across the capital were already being hurt before the vote, with prices decreasing 1.4 percent in May, the biggest monthly decline since June 2011, according to data compiled by Acadata Ltd. and LSL Property Services Plc. The Royal Institution of Chartered Surveyors’ measure of London home-price changes last month fell to its weakest since the financial crisis.

“At the price point above 1 million pounds or 1.5 million pounds, you will find that there is more supply, and therefore from a sales perspective it is more challenging,” Barratt Developments Plc Chief Executive Officer David Thomas said by phone this week.

Prime-home sales dropped 18 percent in the 12 working days after the vote compared with the same period before the referendum, the Lonres data shows. The number of homes under offer fell by a third.