Paramedics took three times longer than official targets to reach a policewoman who suffered a suspected heart attack while responding to a call and later died.
Dc Adele Cashman collapsed in Belsize Park Gardens, Camden, on Monday night.
But a mix-up over location meant it took 23 minutes for an ambulance crew to arrive.
The target time for emergencies is eight minutes. Dc Cashman, 30, died shortly after being taken to the Royal Free Hospital.
A post mortem failed to identify the cause of Dc Cashman’s death.
The officer was a keep fit fanatic and had recently returned from a holiday to the United States.
Coroners are investigating the possibility that she was killed by deep vein thrombosis caused by the long haul flight.
A London Ambulance Service spokeswoman said: “We were called at 9.39pm on 5 November to reports of a woman who had collapsed.
“The caller said the patient had collapsed in Belsize Park. We dispatched an ambulance crew and single responder immediately who were on the scene in five minutes. However, our crews were unable to locate the patient.
“Our control room rang the caller back who said they were actually in Belsize Park Gardens and we redirected our ambulance crews who were with the patient at 10.02pm.
“A further single responder in a car, an officer and a medical team including a doctor and a paramedic also attended.”
