The family of Harry Dunn have begun legal action against the Foreign Office, saying that Anne Sacoolas should never have been given diplomatic immunity.

The American, who has admitted to driving on the wrong side of the road and hitting the teenager, is married to an intelligence officer based at RAF Croughton and therefore says she is not susceptible to prosecution under UK law.

But the Dunn family are arguing that this cannot be the case, because her husband is not a diplomat, but an intelligence officer and does not have the same immunity.

After a meeting at the chambers of human rights barrister Geoffery Robertson QC, Radd Seiger, the family's spokesperson told Sky News: "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 judicial review is a type of court proceeding in which a judge reviews the lawfulness of a decision or action made by a public body.