A London police officer is due to appear in court on Monday, charged with rape.
The Metropolitan Police said serving police officer David Carrick, 46, was arrested on Saturday in Hertfordshire.
The police force suspended him on the same day.
He was then charged with rape on Sunday.
Carrick is a member of the London police unit responsible for the protection of Parliament and diplomatic missions.
The chief of the Metropolitan Police, Cressida Dick, said she was “deeply concerned” by the arrest.
"I am deeply concerned to hear that a police officer from the Parliamentary and Diplomatic Protection Unit has been arrested and charged with this serious offence," she said.
"I fully recognise that this will be of great concern to the public as well."
"Criminal proceedings must now take their course so I am unable to comment any further at this stage," she added.