The worst heritage crime to hit Dover's Western Heights in 40 years has seen irreplaceable pieces from a Victorian road stolen.

Thieves - one man one woman - escaped with 25 wooden blocks after they were spotted going prepared with a ladder.

A volunteer from the Western Heights Preservation Society witnessed the crime.

He saw them accessing the site at the north entrance where the drawbridge crosses the moat.

Despite calling the police, officers arrived too late to catch them and they got away with about 25 of the 160 year-old wooden blocks.

Phil Eyden, a volunteer from the society, warned that if the six inch cubes were stolen for firewood, the thieves could be in for a shock when they strike a match.

"They were organised. They knew what they were doing" - Phil Eyden Western Heights Preservation Society

"Apparently they were impregnated with arsenic so if they are burned then they could be in serious trouble," he said.

He has warned anyone who is offered firewood for sale, to be cautious. If it fits the description, call Kent Police on 101, and certainly don't burn it.

He has also urged residents in the area to keep a close eye on the moats and call the police if they see any suspicious activity.

The blocks are described as being “dozens of six inch cubes that constituted the road surface through the north entrance tunnel".

It is believed they have been there since 1860. They would have been walked upon by troops on their way to the Western Front in the First World War, and Mr Eyden believes soldiers probably trapsed through there on their way back from Dunkirk.

He fears the thefts must have been going on for days because so many have gone.

"Graffiti is bad enough - we can clean that up, but these have gone. They're irreplaceable."

He added: "It does appear this was orchestrated. They were organised. They knew what they were doing."

The crime may have scuppered the hopes of the society, which planned to open the feature to the public at the end of the year.

"Now we might not be able to do that because this is our stable surface gone.

“This is a heritage crime. We are all quite upset about this.”