The wife of a US diplomat has left the UK after becoming a suspect in the police investigation into a fatal road crash.

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

Northamptonshire police confirmed that a 42-year-old American woman being treated as a suspect in their investigations has left the country.

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.”

Speaking to Sky News, Mr Dunn’s mother Charlotte Charles said: “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.”

She added: “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.”

Speaking to the PM programme on BBC Radio 4, Mrs Charles later said her son had “no chance” of avoiding the collision with a vehicle that pulled out on “the wrong side of the road”.

She added: “Harry’s stepdad, my husband, is a US citizen. A couple of weeks or more after we’d lost Harry we let the police know that Bruce, my husband, was a US citizen, in the hope that that would help matters.”

She said 48 hours later, the family received a “basic letter” from US ambassador Woody Johnson, but no contact from RAF Croughton, where United States Air Force personnel are based, or the Ministry of Defence (MoD).

Speaking of the suspect, Mrs Charles said: “We’re really hoping to try to get her back, from me as a mum, to her, as a mum, you just hope that he [Foreign Secretary Dominic Raab] can try to get through to her, that we don’t wish her any ill harm, but we don’t understand how she can just get on a plane and leave our family just utterly devastated.

“If we don’t get any luck over here, then we will go over there.”

A crowdfunding webpage has been set up to provide support to Mr Dunn’s family, including his twin brother Niall.

The gofundme page, that has so far raised just over £1,000, says Mr Dunn was an avid fan of Northampton Town football club whose “love for his family and friends… outshone everything and made him the caring and loving young man he was”.

Family spokesman Radd Seiger told the PA news agency that Mr Dunn’s family are “utterly devastated” and “not coping well at all” following the teenager’s death.

He added: “If that weren’t bad enough, they now have a situation not of their making where the American Government has whisked this American citizen back to the US before they could get some justice.”

In a statement, Foreign Secretary Dominic Raab 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.”