Birdspotter in Scarborough's Falsgrave Park takes photo of the Blue Thunder elite SAS helicopter instead !

The SAS aircraft is nicknamed 'Blue Thunder', after the secretive unit of the same name, and can be dispatched to an emergency situation on the direct orders of the Home Secretary.

The unmarked helicopter was photographed by Joe Bamfield above Scarborough just after midday on Wednesday.

Shortly before that, it was seen over West Yorkshire, believed to be on a training exercise in the Ferrybridge area, and was flying with its transponders switched off, meaning it does not appear on radar or a flight tracking app. It is navy blue with a white underneath.

Joe, a retired joiner, said: "I was out birding in Falsgrave Park when it flew north at 12.12pm. When I checked the images on my computer I noticed it had no identification markings, so I checked the internet and found a Yorkshire Post article about it flying over West Yorkshire.

"I usually photograph wildlife but, using long lenses, planes and helicopters get taken as well, such as American F15 fighter jets that are quite common around here at the moment.

"When I was photographing the peregrines on the castle headland I got some action shots of the lifeboat and air sea rescue helicopter."

In November, the Ferrybridge power station site was used for a 12-hour counter-terrorism training exercise involving staged explosions, gunfire, and a simulated hostage situation.

In June 2017, Blue Thunder was deployed on the UK's streets for the first time when it landed near London Bridge following the terror attack there.

The 70-strong Special Forces squad called Blue Thunder was formed in 2015 specifically in response to the threat from 'lone wolf' attackers, and they rehearse such scenarios regularly.

News of the unit's formation emerged after the Brussels terror attacks, and they are now on standby around the clock. Their deployments are supported by an Apache gunship helicopter.