Police investigating the alleged attempted murder of a constable injured in a hit-and-run have made two arrests.
The on-duty plain-clothes officer was taken to hospital with head injuries after the collision on Tuesday afternoon in Market Square, Aylesbury.
The 30-year-old has been discharged with concussion and is recovering at home.
A 20-year-old man from High Wycombe was arrested in the early hours of Thursday morning on suspicion of attempted murder, Thames Valley Police said.
A 27-year-old woman, who is also from the town, was arrested at the same time on suspicion of assisting an offender.
They are both in police custody.
The officer, who is based in Aylesbury, tried to stop the red Vauxhall Astra but it drove off and was involved in two other collisions before it was abandoned in nearby Osier Way.
The driver and two passengers fled the scene, a force spokesman said.
No-one was injured in the other crashes.
The force reiterated its appeal for witnesses or anyone with information, mobile phone or dash cam footage to call police on 101 quoting 747 (13/2).