The prime minister ‘reiterated the need’ for Anne Sacoolas to be brought back after the US refused an extradition request, No 10 has said.

Harry, 19, died in August last year after his motorbike crashed into a car outside RAF Croughton in Northamptonshire.

Mrs Sacoolas, 42, claimed diplomatic immunity following the crash and was able to return to her home country.

In December, she was charged with causing Harry’s death by dangerous driving by the Crown Prosecution Service.

Despite a determined campaign from Harry’s family, the US have refused to allow Mrs Sacoolas to be returned.

A Downing Street spokeswoman said Mr Johnson had raised the topic during a telephone conversation with Mr Trump yesterday.

She said: ‘The Prime Minister raised the tragic case of Harry Dunn, and the need to secure justice for Harry’s family.

‘He reiterated the need for the individual involved to return to the UK.’

Business Secretary Andrea Leadsom met with Harry’s family yesterday, a day after she had informed them of US Secretary of State Mike Pompeo’s decision to refuse the request.

She also held talks with US ambassador Woody Johnson, the commander of RAF Croughton Colonel Bridget McNamara and the Chief Constable of Northamptonshire Police.

Ms Leadsom, the family’s constituency MP, said she had expressed her disappointment to the US ambassador.

She added that Boris Johnson is ‘very much on the side of the family in their desire to see justice done’.

A spokesman for the US State Department said the request was rejected because it would render the invocation of diplomatic immunity a practical nullity and set an extraordinarily troubling precedent.

However, Foreign Secretary Dominic Raab has claimed the move ‘amounts to a denial of justice’.

The Foreign Office maintains the suspect had diplomatic immunity, which has been disputed by the family.