Locks had to be changed to parts of a research plant containing nuclear material when opportunist thieves stole keys from a car.

The keys were in a briefcase of a member of the emergency response team at the former nuclear facility at Harwell, near Didcot, in Oxfordshire.

A short wave radio from the plant and a mobile phone with the numbers of senior personnel were also taken.

The UK Atomic Energy Authority (UKAEA), which runs Harwell, said the theft posed no threat to the facility.

The car was broken into in a car park at Reading railway station on 23 March but the news has only just emerged.

The UKAEA said the stolen briefcase also contained plans for emergency evacuation of the plant.

Atomic research

It said the stolen keys were to a communications room in a building separate from nuclear and chemical facilities and there was no access to those facilities from that area.

The UKAEA also said the information in the communications room would have been of no use to a terrorist.

Harwell, a former Second World War RAF base, opened in 1945 as a nuclear research centre.

It is now being converted into a business park for science and technology.

The nuclear reactors there are no longer operational and over recent years the UKAEA has been dismantling its nuclear facilities.

But the company confirmed that there is still some nuclear material and nuclear waste on the site.