The wife of a US diplomat has fled the UK after becoming a suspect in a police investigation into a fatal road crash - despite saying she wouldn't.

Harry Dunn, 19, of Charlton, Banbury, died after his motorbike collided with a car near RAF Croughton in Northamptonshire on August 27.

The RAF base is one of the most important bases run by America in Europe.

Northamptonshire police today confirmed that a 42-year-old American woman being treated as a suspect in their investigations, who has not been named, has left the country.

Harry Dunn, 19, was killed on August 27 in a car crash near RAF Croughton in Northamptonshire

It was reported in initial findings by police were that Harry had been driving on the correct side of the road when a woman in a car pulled off of the airbase

The car hit Harry (pictured when he was younger) head-on and he died soon after in hospital after suffering multiple injuries

Superintendent Sarah Johnson 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.

'We are also working closely with the Foreign & Commonwealth Office in an effort to come to a resolution regarding this matter.

'Harry Dunn's family deserve justice and in order to achieve this, a full and thorough investigation, with the assistance of all parties involved, needs to take place.

'Northamptonshire Police is committed to ensuring justice for Harry and specially trained officers continue to support the Dunn family in their loss, including keeping them fully informed of all developments in the investigation.'

It was reported in initial findings by police that Harry had been driving on the correct side of the road when a woman in a car pulled off of the airbase on to the wrong side of the carriageway.

The car hit Harry head-on and he died soon after in hospital after suffering multiple injuries.

Sky News has reported that the suspect involved is the wife of a US diplomat who quickly claimed diplomatic immunity following the incident.

Harry's mother, Charlotte Charles, (left with his father Tim) received a letter of condolence from US Ambassador to the UK Woody Johnson

Tributes have been left for Harry following the crash near RAF Croughton in Northamptonshire on August 27

Speaking to the broadcaster, Harry's mother Charlotte Charles said: 'President Trump, please listen. We're a family in ruin. We're broken.

'We can't grieve. Please, please let her get back on a plane.'

She added: 'Everyone loved him, we're utterly broken inside and out, everything hurts day and night, it's an effort to do anything, I ache from it, every limb, every internal organ hurts.

'We don't know how we can start to grieve for him.

'We have nothing. No justice. We have nothing to put our minds at rest that she's even remorseful.'

Top diplomatic officials are immune from prosecution under diplomatic immunity, as are their deputies and families.

Northamptonshire Police had attempted to apply a waiver that would allow them to continue to investigate and conduct interviews.

But this application was declined.

The car hit Harry head-on and he died soon after in hospital after suffering multiple injuries

She had reportedly pulled on to the wrong side of the carriageway as she left the junction

Foreign Secretary Dominic Raab became aware of the incident and said: 'I wish to offer my condolences to the family affected by this tragic incident.

'I have called the US Ambassador to express the UK's disappointment with their decision and to urge the Embassy to re-consider it.'

In its own statement provided to Sky News, the US Embassy in London offered its 'deepest sympathies' to Mr Dunn's family following the accident 'involving a vehicle driven by the spouse of a US diplomat assigned to the United Kingdom'.

It added: 'Embassy officials are in close contact with the appropriate British officials on this matter.

'Due to security and privacy considerations, we cannot confirm the identity of the individuals involved, but we can confirm the family has left the UK.'

Harry's parents, Tim Dunn and Charlotte Charles, have received a letter of condolence from US Ambassador to the UK Woody Johnson.

In it he said that 'it is with profound sadness' that he offered his condolences to the family but Mr Johnson made no reference to responsibility.