Police failed to arrest an American spy after she killed at teenage motorcyclist while driving on the wrong side of the road because they prioritised her welfare over a 'prompt and effective investigation', a damning review has found.

Anne Sacoolas fled back to her homeland under cover of diplomatic immunity 19 days after being allowed to leave the scene of the head-on collision that left 19-year-old Harry Dunn fatally injured.

The August 2019 collision happened just 30 seconds after the mother-of-two had driven out of a US air base in Northamptonshire, where Sacoolas had enjoyed a barbecue with her husband Jonathan, a diplomat, and their children.

Harry's family launched a three-year fight for justice which culminated in Sacoolas being handed a suspended sentence at the Old Bailey after pleading guilty via videolink from Washington to causing death by careless driving.

Now a review into Northamptonshire Police's handling of the investigation, commissioned by chief constable Ivan Balhatchet, has found officers allowed Sacoolas, now 47, to be driven home by her husband because they believed the 'necessity test' had not been met for arrest.