They call them yellow vultures - but they haven't swooped once.

Eastern Daily Press: Average speed cameras have not been switched on six months after they were installed on the A149 Picture: Chris BishopAverage speed cameras have not been switched on six months after they were installed on the A149 Picture: Chris Bishop (Image: Archant)

Not one errant driver has been caught by average speed cameras six months after they were installed because they haven't been switched on yet.

The devices were put up along the A149 between King's Lynn and Snettisham in July.

Norfolk's police and crime commissioner Lorne Green said: "I gather there's been some technical problems but it's been far too long, I think it's unacceptable."

The area covered includes Babingley, where the Duke of Edinburgh was involved in a collision in which his car overturned six months earlier.

Eastern Daily Press: The Duke of Edinburgh's car after the crash on the A149 Picture: Chris BishopThe Duke of Edinburgh's car after the crash on the A149 Picture: Chris Bishop (Image: Archant)

MORE - Duke unhurt after car overturns in crash

But some of the cameras have not yet been connected to the power supply meaning the system is not operational. Engineers have been seen connecting power cabling to the cameras on Knights Hill.

A Norfolk County Council spokesman said it was not normal to "partially install" cameras.

They added: "In this case we installed the cameras but it took longer than anticipated to establish the power supply. These issues have now been resolved."

the county safety partnership is planning to go live with the cameras on Monday.

One senior source said the cameras had already done a successful job of deterring speeders.

The county council agreed to put up the cameras at a meeting days after the Duke's crash on January 17.

The scheme had been under discussion for months beforehand.

Councillors also agreed to reduce the speed limit from 60 to 50mph between Babingley and Dersingham.

But the proposals have not yet gone out to public consultation.

A council spokesman said: "A public consultation is also being launched on Friday, February 21 with proposals to implement a 50mph speed restriction on two sections of the A149.

"More information will be made public in due course to ensure people know how they can let us know their views."

There is no suggestion speed was to blame for Prince Phillip's crash. The 98-year-old Royal said he was dazzled by the low setting sun and pulled out into the path of an oncoming car.

The Duke walked away shaken but uninjured, while two women travelling in the other car involved in the incident suffered minor injuries.

Prince Phillip had been living at an estate cottage near the scene of the crash since retiring from public life in 2017. He later agreed to voluntarily surrender his driving licence.

Data shows that in the six year period to the end of August 2019, there were 34 personal injury collisions recorded on the A149, including three fatal and 10 serious. The previous period was six years to the end of May 2018 in which there were 40 collisions including five fatal and 10 serious.