Zoo and quarry company 'threaten key Roman site' near Colchester

Colchester Zoo, home to more than 160 species, is planning to expand

A zoo and a quarry company are putting an Iron Age earthwork at risk, according to heritage experts.

Historic England said Tarmac's plan to extract 500,000 tonnes of sand and Colchester Zoo's expansion plan could harm Gryme's Dyke.

The organisation said the dyke in Essex was a monument of "the highest significance".

Tarmac insisted there would be no material impact on the dyke. The BBC has invited the zoo to respond.

Tarmac wants to extract about 500,000 tonnes of sand at its Stanway Quarry

The protected ancient monument of Gryme's Dyke in Stanway Green was one of a number of large linear earthwork dykes to define and protect the important settlement centre of Camulodunum - modern-day Colchester.

It may have been built just after the Roman invasion in AD43, possibly as part of the response to the revolt led by Boudica when the town was destroyed by fire.

Tarmac wants to dig a southern extension to Stanway Quarry next to the zoo, which is developing its own plan to expand alongside the quarry's proposal, according to the Local Democracy Reporting Service.

The quarry extension will support Colchester Zoo's plans to expand

The zoo said it supported the Tarmac application, which is being promoted as enabling work for the future expansion of the zoo.

Dr Jess Tipper, Historic England's inspector of ancient monuments for Essex and Hertfordshire, said: "The proposed development would permanently change the setting of the scheduled Gryme's Dyke.

"[It} would result in harm to the appreciation and experience of this heritage asset of the highest significance. This is contrary to policy for sustaining and enhancing heritage assets."

The zoo supports the plan to extend the quarry

However, Tarmac said: "There will be no material changes to topography and no material change to the setting of the scheduled Gryme's Dyke, and thus no significant impact.

"The proposal incorporates important enhancement measures that will ensure the asset is not further degraded by agricultural activity."

The zoo, which has been approached for comment, has said its expansion plans would create jobs.