The Press Association has reported that the man arrested is Iranian.

Faslane is one of the U.K.’s largest and most sensitive military sites, and is not open to the public.

While it is not known what the pair’s motive was, the incident comes amid heightened concerns about hostile activity from Iran in Britain.

Faslane is home to all of the Navy’s nuclear submarines, including the Vanguard-class ballistic missile submarines which carry Trident nuclear missiles.

The site is protected by Ministry of Defence Police and Royal Marine Commandos, which were scrambled to their highest alert yesterday, according to the Sun.