A woman has appeared at a UK court to face a charge of causing the death of British teenager Harry Dunn by dangerous driving, ending his family's three-year wait for criminal proceedings to begin.

Anne Sacoolas made an appearance at Westminster Magistrates' Court via video-link from the US as the 19-year-old's extended family watched from the public gallery.

The 45-year-old is accused of causing the teenage motorcyclist's death following a collision outside a US military base in Northamptonshire in August 2019.

Ms Sacoolas had diplomatic immunity asserted on her behalf by the US government following the collision outside RAF Croughton, and was able to leave the UK 19 days after the incident.

At the six-minute hearing, the defendant spoke only to confirm her name and date of birth as she followed proceedings next to her lawyer, Amy Jeffress.

Mr Dunn's parents Charlotte Charles and Tim Dunn, alongside his twin brother Niall, arrived wearing either a green tie or a green scarf in memory of the teenager.

The Dunn family told the PA news agency they would not be commenting on the case until the conclusion of criminal proceedings.

Ms Sacoolas was granted unconditional bail.

She was told by the chief magistrate at Westminster Magistrates' Court she must attend the next hearing at the Old Bailey in person.

The court heard there would be a joint application from both the prosecution and defence for Ms Sacoolas to appear via video-link again on October 27.