Police are coming under mounting pressure to reveal details of a mysterious spyplane said to eavesdrop on mobile phone calls.
A radar tracking website showed an aircraft circling London at 10,000 feet for more than two hours yesterday.
The plane had no recognisable callsign but was identified as a twin-engine Cessna F406 with the registration G-BVJT.
The aircraft has also been operating in other parts of the UK. Its movements over Leicester were captured by a flight tracking website in May.
The aircraft has been linked in the past to shadowy fleet of surveillance planes said to be operated by the Metropolitan Police.
Darren Burn, who lives beneath the flight path says he also saw a second spyplane.
Reports suggest the two planes, costing £3m a year, are used to monitor mobile phone calls.
The Liberal Democrats have called on Boris Johnson as head of the Mayor's Office for Policing and Crime to explain the cost and role of the aircraft.
But last month the mayor replied:
The video below shows the same plane taking off earlier this year in Cambridge.
Caroline Pidgeon, a Liberal Democrat member of the London Assembly said: