He had worked in the North West Basic Command Unit in London.
The Met said Bedfordshire Police arrested Mr Benson on suspicion of sexual assault in November 2020, but in September 2021 he was informed no further action would be taken.
Bedfordshire Police then contacted the Met’s Directorate of Professional Standards and a misconduct investigation was launched which concluded on Friday that Mr Benson had breached the standard of professional behaviour at the level of gross misconduct, the force said.
Det Supt Will Lexton-Jones said: “My thoughts are first and foremost with the victim who displayed courage in reporting this.
“PC Benson’s abhorrent behaviour has led to his immediate dismissal, which is a decision I fully support.
“I hope this outcome demonstrates how we are rooting out those who do not demonstrate the high standards we demand from our officers.”
