Activists blockade part of A692 between Leadgate and Dipton

A number of people were arrested at the Bradley site, between Leadgate and Consett, at the weekend and two are understood to remain 'locked on' to prevent work to access the site.

A 23-year-old man, from Cambridgeshire, and a woman, whose details are yet to be released, were arrested on suspicion of obstructing the highway.

Two men, aged 37 and 38 from Newcastle, were also arrested on suspicion of assisting an offender.

A Durham police spokesperson said last night that the four remained in custody, while two further people who arrived on Sunday were still ‘locked on’ at the site.

A 21-year-old woman, who is a foreign national, was also arrested on Saturday to prevent a breach of the peace and is due at Newton Aycliffe Magistrates’ Court this morning.

The A692 outside the site was reduced to one lane over the weekend as part of upgrading works which were due to be completed yesterday but were delayed due to the protest activity.

A traffic management system will remain in place to allow the work to be completed.

Chief Inspector Catherine Clarke, from Durham Constabulary, said: “We would like to thank the local community for their patience during this weekend’s operation, and to apologise for the prolonged disruption it has caused as we dealt with the incidents.

“The behaviour we have seen this weekend, which we have previously raised concerns about, continues to affect the day-to-day policing of our communities and is having a financial impact on Durham Constabulary and its partners.”

The activists, who have held repeated demonstrations at the site, arrived again at around 8.30pm on Saturday night. 

One of the protestors said: “I spent four years studying the science behind climate change. Today, I am taking the data to its logical implications. Coal has got to stop. My actions are necessary.”

Members of the County Durham and Darlington Fire and Rescue Service, were called in by Durham Constabulary to help with the "slow and meticulous operation" to expose the 'lock-on' device with cutting equipment.

A spokesman said at 6pm on Saturday: "It's incredibly intricate and time consuming. We expect to be here a few hours yet."

Campaigners say they disapprove of the involvement of the fire brigade in the police action.

They argue that a specialised cutting team should be dealing with the lock-on devices, as the lives of the protestors are not being endangered. 

They add, police have refused to find specialist cutters. 

An earlier demonstration on Saturday saw dozens of members of the of the Campaign to Protect Pont Valley lining the road.

Banks Mining, a division of The Banks Group, has permission to extract about half a million tonnes of coal. The firm says that work to dig up the coal has started, meaning that planning permission has been triggered.

But opponents to the scheme say the conditions of the planning consent are being breached because an access road is not yet built.

Permission for the opencast was granted to UK Coal on June 3 2015. The planning permission expires if not triggered within three years, with the deadline today.

Campaigners argue that to trigger planning condition a developer must meet all the pre-commencement conditions listed in the Section 106 agreement and in the appeal decision conditions – stating that that work on the site shall not commence until the access road has been built.

Banks have also been accused by the protesters of wildlife crimes, after a great crested newt was said to be found on the site.

The company says operations planned at the site have thoroughly considered all environmental matters including ongoing checking surveys by independent ecologists.

It argues the "project will create multiple new habitats for newts and other species".

The weekend's protest, amidst a strong police presence, came after three protestors prevented the delivery of tarmac to the site. They did so by securing themselves to improvised lock-on devices and laid in the road in front of Tynedale Roadstone on the Newburn Haugh Industrial Estate, in Newburn, Newcastle.

But after several hours on Friday, company workers at the firm created an opening in their security fence at the back of their premises and created a way for lorries to reach a nearby road.

Banks has said a programme of work to make highway improvements around the new Bradley surface mine is being extended to include the reconstruction of a few hundred yards of road.

The company has a temporary traffic management system in place as part of the upgrading works required to provide access onto the Bradley site.

A three-way traffic light system along the A692's junction with the A693 was put in place to allow for the tarmac work to be carried out on Saturday, causing long tailbacks of traffic.

The company says the traffic lights will be manned during peak times to ensure that traffic is able to flow as smoothly as possible.

Evening road closures between the Jolly Drovers Pub roundabout and the junction for the A693 will also be introduced between 7pm and 6am for four nights from Monday.

Lewis Stokes, community relations manager at The Banks Group, said: "We have planned the highways work required around the Bradley project carefully in adherence with Durham County Council, and have put all possible measures in place to undertake it as quickly and efficiently as we can, so as to minimise disruption to local traffic."

Stuart Timmiss, head of planning and assets at Durham County Council, said earlier this week: “The S106 agreement referred to requires the protected right hand turn works to have been completed prior to the commencement of soil stripping. As these highway works have not yet been completed, the S106 requirements have not been met.

“However, as the S106 is a separate agreement to the planning permission, a breach of it does not constitute a breach of the planning conditions and does not stop an approval being implemented. It is however a matter which we are actively pursuing with Banks.”