The mystery surrounding a huge police convoy that is thought to have travelled through Kent has been solved.

Shocked motorists on the M25 spotted the enormous fleet of cars and vans which appeared to be escorting a truck carrying a huge, covered object.

Watch: the mysterious transport and police convoy

The convoy, which also appeared to include highways vehicles, is thought to have first been seen leaving the county into Essex.

One eyewitness, who picked the trail up around Junction 30, near Thurrock in Essex, said vehicles were stopped from overtaking immediately.

"There must have been hundreds of police officers overall, every junction had two van loads join as it passed," he said.

"I was stuck behind it for an hour because they were only letting one car past at a time so it took ages to pass.

"I joined it at Junction 30 but I'm sure it came from Kent. They were transporting a massive lorry, really big with a number of wheels."

Following a KentOnline story yesterday, internet sleuths were quick to try and track down the possible reasons behind the transport.

There was speculation it could have been the transportation of nuclear warheads or parts from the decommissioned power station at Dungeness, while some thought gold might have been behind the canvas.

One even hazarded a guess that the precious metal on the truck would be worth more than £65 million pounds, while another said readers should be more open to the possibility that it might be hiding a UFO.

However, the mystery has now been solved after an Essex Police spokesperson confirmed the officers were escorting the transportation of equipment for the HS2 project.

Details remain scarce, but it is known that the convoy was co-ordinated by the Metropolitan Police.

The Met has been contacted for comment.