Questions from coroner at M4 inquest: our full coverage

Why did a school minibus full of pupils and support staff suddenly stop without warning on the M4 motorway, causing a lorry to smash into it with the loss of three lives?

That's the question a Coroner raised at an inquest into the deaths of three members of staff at Prior's Court School at Hermitage, near Newbury. Heidi Connor is writing to the motor company, Ford, to ask it to re-examine the vehicle.