A woman was found wandering around the Houses of Parliament in the middle of the night after reportedly locking herself into a toilet cubicle at the end of a walking tour.
The visitor did not emerge from her hiding place until around 2am on Sunday, before she began to go walkabout, the Daily Mail reported.
She was apparently found in Westminster Hall by security officers who then alerted the police.
Parliamentary officials have begun a probe into the security lapse while a police investigation is also under way.
A Metropolitan Police spokesperson said: “In the early hours of Sunday, 7 June, a woman in her 50s was arrested on suspicion of trespassing - breaching a section of the Serious Organised Crime and Police Act 2005 - after remaining in the Palace of Westminster for several hours following the conclusion of an organised tour.
“She was released on bail pending further enquiries.”
A Parliamentary spokesperson said: “A member of the public was arrested for trespassing on the Parliamentary Estate on Sunday 7 June. The incident is now being dealt with by the Metropolitan Police.
“The safety and security of all those who work and visit in Parliament is our top priority. Whilst we cannot comment on our security processes or measures, a review is underway following the incident.”
