British police will travel to the U.S. to question Anne Sacoolas, the American at the heart of a dispute over diplomatic immunity that's only getting bigger. Harry Dunn, 19, was on his motorcycle in the U.K. when he was hit by Sacoolas, the wife of an American official in Britain. Sacoolas was driving on the wrong side of the road when she hit Dunn. She later left the U.K. under diplomatic immunity.

In a press conference Monday night, police said Sacoolas requested to be interviewed by investigators in person. Sacoolas was last questioned by British investigators on August 28, a day after the fatal accident and also when police learned she could be protected under diplomatic immunity.

On September 16, authorities became aware she had left Britain, possibly in a U.S. Air Force plane, but it wasn't until 10 days later that the Dunn family were told she had returned to the U.S.

Now, Britain's Foreign Secretary is questioning whether the diplomatic immunity Sacoolas used to leave the U.K. should be guaranteed for the approximately 16,000 American personnel and their families at the airbase where Sacoolas lived.

Dunn's death sparked an extraordinary campaign for justice that has already seen his family travel to the U.S. and meet President Trump. They could have met Sacoolas, too, who was at the White House during their visit with the president, but declined the encounter.

The couple said they felt the time and place to meet Sacoolas was wrong, and they have continued pushing for her to return to Britain to face justice.

Harry Dunn's family told CBS News correspondent Imtiaz Tyab that the British police interview will be a step in the right direction, but until Sacoolas turns herself in, they're not giving up.