The family of teenager Harry Dunn have lost their High Court legal challenge against the Foreign Office.
Harry, 19, died when his motorbike crashed into a car driving on the wrong side outside a US military base RAF Croughton in Northamptonshire in August 2019.
The driver American Anne Sacoolas, whose husband Jonathan worked at the base, left the country a few weeks later after the US said she was entitled to diplomatic immunity.
Harry’s devastated parents Charlotte Charles and Tim Dunn claim the Foreign, Commonwealth and Development Office (FCDO) wrongly decided Mrs Sacoolas had diplomatic immunity and unlawfully obstructed Northamptonshire Police’s investigation.
The mum-of-three has been charged with causing death by dangerous driving and her lawyers say she accepts responsibility.
Harry’s family have fought to have Mrs Sacoolas brought back to the UK to face a jury but the previous Trump administration refused to extradite her.
She is now subject to an Interpol Red Notice, meaning she could be arrested if she leaves the country.
Lord Justice Flaux and Mr Justice Saini delivered their judgment remotely on Tuesday morning.
The Prime Minister Boris Johnson’s official spokesman told Mirror Online: “Our thoughts are with Harry’s family.”
Asked about his parents being pursued for the costs of the judicial review, the spokesman said: “My understanding is that parties have reached an agreement under which Harry’s family will be protected from paying high costs to the Government in respect of the High Court proceedings.”
On the first anniversary of her son’s death Ms Charles pleaded with Mrs Sacoolas to “do the right thing” and hand herself in.
She said: “Just do the right thing and end my torture.
“Then you can move on with your life and we can start to rebuild ours.
“Set a good example to your children by picking up the phone and getting this sorted for your sake and ours.”
She added Mrs Sacoolas could do something else that may help.
“It’s never too late to reach out to say sorry,” she said.
“If the apology was sincere, that one word would mean a huge amount to me.”