Harry Dunn family refer Northamptonshire Police to IOPC

Mr Dunn, 19, died outside RAF Croughton when his motorcycle was involved in a collision with a car driven by US citizen Anne Sacoolas whose husband is a US intelligence official working at the base.

Though she initially cooperated with the police investigation, admitting she was driving on the wrong side of the road, Mrs Sacoolas later left the UK, claiming diplomatic immunity.

In a statement, the spokesman for Mr Dunn’s family, Radd Seiger, said it was “unfortunate” that the family was having to take this action against Northamptonshire Police but that there were “deep concerns about the manner in which this investigation was conducted”.

He added that the fact that Northamptonshire Police had not yet disclosed all the information related to the case “simply adds insult to injury to this family at their darkest hour.”

A Northamptonshire Police spokesperson said the force would be happy to support the IOPC with any concerns raised by the family.

Earlier this week, during a press conference on the case, Chief Constable Nick Adderley said Northamptonshire Police had at all times “acted with the utmost integrity and transparency”.

This latest development was announced on Thursday afternoon (October 24), after members of the family met with human rights barrister Geoffrey Robertson. Mr Seiger told Sky News: “It was a very detailed, thorough and lengthy meeting and there are a number of things that have come out of that.

“The first action we will be taking is against the Foreign and Commonwealth Office. We will be shortly issuing what is called a letter of claim which is a prelude to a judicial review.

“We are absolutely clear that the Foreign Office’s decision to advise Northamptonshire Police that Mrs Sacoolas had the benefit of diplomatic immunity was unlawful and we will be seeking a judicial review of that decision to have it quashed.”

A GoFundMe page set up to collect donations to pay for the legal action has so far raised more than £70,000.

Both the British and US governments have agreed that by returning to the US, Mrs Sacoolas forfeited the right to diplomatic immunity.

Officers from Northamptonshire Police are to travel to the US to interview Mrs Sacoolas under caution at her request. However, the family believes she should return to the UK to face justice.

Mr Seiger said: “It’s absolutely clear that Mrs Sacoolas was involved in a very serious collision that ended in the loss of Harry’s life.

“We are clear she’s admitted her culpability, that she … committed a very serious crime that night. At the very least careless, causing death by careless driving and at the worst causing death by dangerous driving. She is a fugitive from this country and she is on the run.”