Harry Dunn’s parents have said “all we want is for Anne Sacoolas to come back” ahead of their first court battle with the Foreign Secretary.

Charlotte Charles and Tim Dunn told the PA news agency that it was “clear” to them that “something went badly wrong in London” before their son’s alleged killer left the UK.

Mr Dunn’s parents are set for their first High Court hearing with Dominic Raab and Northamptonshire Police in which they allege the Foreign Secretary acted unlawfully over Sacoolas’s departure.

Harry Dunn
Foreign Secretary Dominic Raab has been criticised by the Dunn family (Stefan Rousseau/PA)

At a preliminary hearing on Thursday, conducted remotely via Skype, they will ask Lord Justice Flaux and Mr Justice Saini to order the Foreign Office to disclose further evidence ahead of a full hearing.

Mrs Charles and Mr Dunn allege that the suspect – in line with agreements made between the UK and the US – should have had her claim to immunity pre-waived.

In a so-called “Exchange of Notes”, the two countries appear to agree that privileges and immunities under the Vienna Convention on Diplomatic Relations applied to administrative and technical staff, including Sacoolas’s husband Jonathan, at RAF Croughton in Northamptonshire.

The series of letters goes on to say the agreement was “on the understanding that the United States Government… waives the immunity from criminal jurisdiction of these employees in respect of acts performed outside the course of their duties”.

The Foreign Office argues that – because Sacoolas was notified to them as a spouse – and dependants were not mentioned in the Exchange of Notes, her immunity was not pre-waived, in what they have described as an “anomaly”.

Harry Dunn death
Harry Dunn’s family dispute Anne Sacoolas’s claim to diplomatic immunity (David Mirzoeff/PA)

The diplomatic row started shortly after Mr Dunn was killed when his motorbike crashed into a Volvo outside the US military base.

Sacoolas, 42, claimed diplomatic immunity following the crash and was able to return to the US.

She was charged with causing death by dangerous driving in December but an extradition request was refused by the US the following month.

Mr Dunn’s family also claim that the Foreign Office advised Northamptonshire Police that Sacoolas had immunity – meaning they could not properly investigate the matter.

In a statement to PA before their first court hearing, Mrs Charles and Mr Dunn said: “We lost our son Harry almost 10 months ago. This is not a dispute we wanted or of our making.

“We couldn’t believe when Anne Sacoolas was allowed to leave the UK and still can’t believe it now.

“We know the American government are responsible for that. You do not get to kill someone and walk away.

“However, it is clear to us that things went badly wrong in London too and that the UK Government allowed her to leave unlawfully.”

Speaking about their case, the teenager’s parents added: “We are advised that Mrs Sacoolas did not have diplomatic immunity.

“We have met several times with senior Government members to try to work with them to get to the truth and find a way forward.

“They have chosen to mislead us at every turn and have tried to cover things up instead of work with us.

“We will do everything we can to help the court reach the right decision.

“All we want is for Mrs Sacoolas to come back and face up to what happened and to ensure this never happens to another family again.”

The Foreign Office have maintained that they acted properly and lawfully throughout the case.