They are usually seen flying emergency missions through faraway warzones.

So park walkers got a fright when an armoured Chinook helicopter embarked on a surprise landing in Parliament Hill fields.

Amazed walkers told of their shock as the military chopper with distrinctive double blades, often used on missions in Iraq and Afghanistan, circled for several minutes before touching down in the busy park last Friday afternoon (October 28).

Lewis Dediare, who was cycling through Parliament Hill when he spotted the military operation, said: “I was coming up from Swains Lane when I suddenly heard loud machine hovering over Hampstead Heath.

“At first we though it was Prince William on a royal visit.

“I have never seen anything like it in central London before.

“It was actually a bit scary, the thunderous sound of the chopper flying over feels like something deep in your chest.

“I said to the chap standing next to me that it looks as if there is going to be a war.

“It wasn’t a very bright day, and quite bizarre and disconcerting to see.”

A group dressed in army and naval uniforms descended from the aircraft after it landed.s

They spoke to the hundred or so people who had gathered around to find out why the helicopter had landed.

Mr Dediare added: “There were dozens of children all amazed that the helicopter had landed.

“Earlier this year, when I was flying my kite on the hill, I did see what looked like a Chinook flying overhead during President Obama’s visit to London.

“But that was the closest I’ve seen one in London. But this one actually landed. It is incredible.”

An RAF spokesman said: “We can confirm that an RAF Chinook based Odiham in Hampshire landed at Hampstead Heath on Friday afternoon as part of an authorised training sortie.

“It was part of a training flight to do with a medical emergency scenario.”