An alleged rape in Parliament is being investigated by police.
Scotland Yard said that a 23-year-old had been arrested on suspicion of rape following the alleged attack in the early hours of Friday.
The man arrested is Sam Armstrong, chief of staff to South Thanet MP Craig Mackinlay, ITV News understands.
The office of the Kent MP said in a statement: "Mr Mackinlay was made aware of an allegation against a staff member and granted permission for the police to access his Westminster office.
"Mr Mackinlay is monitoring the situation and awaits further details from the police and parliamentary authorities."
A Met Police spokesperson said: "Detectives from the sexual offences, exploitation and child abuse command are investigating an allegation of rape at the Houses of Parliament in the early hours of Friday, 14 October".
Armstrong has now been bailed pending further inquiries to a date in mid-January 2017.
A House of Commons spokesman said: "We are aware of an incident on the parliamentary estate which is being investigated by the Metropolitan Police Service.
"Parliament is working closely with the police on their investigation and we cannot comment further while this is ongoing".