The high value of the pound against the dollar is deterring US visitors to Britain, with figures for the three months to June showing a 6% fall in arrivals from North America compared with last year.

This follows a 4% drop in the first quarter, with the exchange rate stuck above $2 to £1.

The heightened security at airports since last August, and consequent queues and delays, may also be having an impact on the total number of visitors to the UK, which is down 3% to 8.1 million in the quarter.

A spokesman for national tourism agency VisitBritain confirmed: “The exchange rate is biting now.”

Forward-booking figures from trade organisation UKinbound also suggest falling demand.