A 42-year-old American woman suspected of being involved in a fatal crash in Northamptonshire has left the country after claiming diplomatic immunity.
19-year-old Harry Dunn died in August after his motorbike was hit by a car near RAF Croughton, an American communications base in Brackley.
He was left with multiple injuries and later died in hospital.
Harry's family have been told the car was being driven on the wrong side of the road at the time of the crash.
On the Justice4Harry Facebook page, Harry's parents have released a statement, calling on the unnamed woman to return back to the UK to face trial.
The Foreign secretary Dominic Raab said he has spoken to the US Ambassador and is calling for the woman to return to the country.
"I wish to offer my condolences to the family affected by this tragic incident", he said.
"I have called the US Ambassador to express the UK’s disappointment with their decision, and to urge the Embassy to re-consider it."
Superintendent Sarah Johnson from Northamptonshire Police said: “Northamptonshire Police followed all of its usual procedures following the incident, including liaising closely with the suspect, who engaged fully with us at the time and had previously confirmed to us that she had no plans to leave the country in the near future.
“Due process was also followed in seeking the necessary documentation to allow for the arrest and formal interview of the suspect, and the Force is now exploring all opportunities through diplomatic channels to ensure that the investigation continues to progress."