A London Ambulance crew was sent 200 miles to Manchester by a faulty satellite navigation system while transferring a patient to hospital.
The team were supposed to take the man from King George Hospital in Ilford to Mascalls Park Hospital in Brentwood.
But they did not realise their equipment was faulty until the reached the outskirts of Manchester.
London Ambulance said the patient was in a comfortable condition throughout the eight-hour journey.
The patient left the King George Hospital for the Mascalls Park Hospital, which is a 12 mile (19.3km) journey, in the early hours of Tuesday morning but did not arrive until the afternoon, having travelled to Manchester and back.
The spokesman said: "We believe the crew, who had not been to this particular hospital before, followed the directions given by the navigation system, without manually confirming their destination.
"We understand that they reached the outskirts of Manchester before realising they were heading to the wrong destination. The problem with the navigation database is also now being fixed."