Police have arrested five people after anti-nuclear protesters got inside a military base in north-west London.
The protesters entered Northwood, the British military headquarters for planning and controlling overseas operations, at about 0730 BST.
The three men and two women, from the Trident Ploughshares group, said they wanted to highlight what they claimed was a lack of security at the base.
The Ministry of Defence (MoD) confirmed there had been a security incident.
But a spokesman said the intruders had only managed to breach "initial security" before they were caught.
'Hypocrisy and secrecy'
"After every incident, security is obviously looked at to see if lessons can be learned," the MoD spokesman said.
The three arrested men were a 30-year-old from Islington, north London, an 18-year-old from Powys, in Wales, and a 42-year-old from Doncaster.
The two women who were arrested were a 26-year-old from Highbury, north London, and a 29-year-old woman from Hornchurch, Essex.
Trident Ploughshares said the break-in had been timed to mark the release of Israeli nuclear whistleblower Mordechai Vanunu on Wednesday.
Joss Garman, a spokesperson for the group, said:
"Today, we acted to continue with the vital work started by Vanunu, and to expose the hypocrisy and secrecy that is government policy towards Britain's own Weapons of Mass Destruction."
Hertfordshire Police, which cover the base, said the five people were arrested on suspicion of criminal damage.