A lone protester has been joined by at least five other peace campaigners at one of Britain's high-level spy bases.
More than 100 Greenpeace activists broke into the US-run Menwith Hill base in North Yorkshire yesterday.
Overnight specialist police teams managed to remove most of the protesters who had chained themselves to buildings - but one activist, named Ricko, managed to evade officers.
The activists are demonstrating against the controversial Son of Star Wars missile defence shield.
Greenpeace spokeswoman Ms Louise Edge said Ricko was on the roof of the radar building with a number of other campaigners but managed to evade police officers and was able to climb up one of the directional masts.
"He's now 60 metres up in the air, well out of the clutches of the police, and although he's cold his spirits are high," she said.
Ricko, a Greenpeace worker from New Zealand, has been joined on the base by five or six more campaigners who managed to "re-invade" the site.
The Ministry of Defence has refused to comment on the ease with which large numbers of Greenpeace supporters breached the security but confirmed four arrests were made yesterday.
Two were for criminal damage and one for possession of an offensive weapon. No details were available on the fourth arrest, she said.
PA