Armed police have for the first time tested a scenario where an attempt is made to attack and steal a shipment of radioactive material being transported from the Dounreay nuclear power plant.

The Civil Nuclear Constabulary exercise involved armed attackers deliberately crashing a car to stop a lorry reaching Georgemas Junction, a railway station about six miles from the plant on the north Caithness coast.

In real-life situations, the station has been used for transporting radioactive material from Dounreay to Sellafield in Cumbria for reprocessing or storage.

The training exercise included an employee at Dounreay, near Thurso, being "arrested" in connection with the attack.

The Civil Nuclear Constabulary (CNC) worked with Police Scotland and other emergency services during the exercise held late last month.

A workshop was also held involving police, Highland Council, Dounreay and the Vulcan Naval Reactor Test Establishment.

Vulcan, which sits next to Doureay, is a military facility used for testing prototype nuclear reactors for submarines. CNC said months of planning went into preparing the exercise.

Exercise and resilience manager Steve Warren said: "This was a scenario that had not been exercised or tested before, meaning we were asking a lot of everyone involved." Ch Insp Dave McIntosh, of Dounreay's operational policing unit, said the training had placed personnel in "really challenging circumstances".

He added: "I'm very proud of them, they did a really, really good job." Dounreay was built as an experimental nuclear reactor site in the 1950s and is now in a years-long process of being decommissioned.