A police officer is in a critical condition in hospital after being run over by a car driven by a suspect she was attempting to arrest.
Police said they were treating the incident, which happened soon after 8am outside the Sheraton hotel in Hayes, west London, as attempted murder.
Tonight, Scotland Yard said a 41-year-old man had been arrested in the West Midlands in connection with the hit and run.
Detective Constable Catherine Corbett, a 39-year-old from the West Midlands police, had been in the capital in connection with an ongoing fraud investigation.
"It is believed that the officer was attempting to arrest a man in connection with a West Midlands police investigation," a Metropolitan police statement said.
"The suspect decamped from the scene in a car which was in collision with the officer, who was on foot. The suspect's vehicle then collided with another vehicle before driving off."
The officer was taken to a north London hospital with serious head injuries. The suspect's car, a blue Peugeot 207, was later found abandoned.
"We can confirm that a female officer has been seriously injured this morning in the Hayes area of London while attempting to arrest a man in connection with a West Midlands police investigation," a spokesman for the West Midlands force said.
"The female officer was with a team from West Midlands police in Hayes to effect an arrest in connection with an ongoing fraud investigation."
A number of the officer's West Midlands colleagues were with her at the time of the incident. Two, both male, suffered minor injuries and were treated at the scene.
DC Catherine Corbett was seriously injured in the incident.  

A 42-year-old man and a woman in her thirties have been arrested after a police officer was left critically injured after being hit by a car as she tried to make an arrest in west London this morning. 

Police are treating the incident as attempted murder.

Detective Constable Catherine Corbett of West Midlands Police was trying to arrest a man at Sheraton Hotel, near Heathrow Airport when the suspect escaped by car and left the officer with head injuries. She was in London as part of a fraud investigation. 

The man was arrested by firearms officers in Birmingham and will be taken to London for questioning. The woman has been held after she contacted the police.

Speaking about Corbett, Assistant Chief Constable Gareth Cann said, "Cathy is an experienced police officer and a very good police officer."

Police have appealed for anyone with any information to contact the Metropolitan Police Incident Room on 020 8358 0400 or Crimestoppers anonymously on 0800 555 111.