A farmer has been found guilty of killing a woman in a crash while driving a tractor on a country road in Norfolk.

Henry Bett is the son of Stephen Bett, the former Tory chairman of Norfolk Police Authority, who now serves as the independent police and crime commissioner (PCC) for the county.

The 26-year-old, of Hall Lane, Thornham, Norfolk, denied causing death by dangerous driving but a jury at Peterborough Crown Court sitting in Huntingdon found him guilty after four hours of deliberations.

Mother-of-two Rebecca Brown, 43, died when the Fiat people carrier she was driving was crushed in a collision with Bett's Fendt tractor on a country road in Norfolk.

During the trial, the court heard he may have been experiencing a 'comedown' effect after taking cocaine several days earlier.

Speaking after the jury delivered its verdict, prosecutor Simon Wilshire told the court Bett is being investigated for a separate allegation of speeding and careless driving.

This relates to an incident involving his Land Rover on June 20 - about six weeks before the trial began. No charges have been brought.

Bett also has three speeding endorsements from 2011.

Adjourning the case until August 20 for sentencing, Judge Peter Murphy warned Bett a prison sentence was 'extremely likely'.

Bett looked shocked as the verdict was delivered while Mrs Brown's widower sobbed in the public gallery.

Mrs Brown's son Thomas, who was 17 at the time, was in the car when the crash happened on West Acre Road near their home village of Castle Acre at about 3.10pm on December 4 2013.

He, along with Bett and members of the public, fought to save her life but she died at the scene.

The prosecution said Bett was speeding, driving in the middle of the road and failed to brake. The impact of the collision crushed Mrs Brown's car.

Giving evidence, Bett said he believed he had been driving at the 20mph speed limit for tractors.

He said he was horrified that Mrs Brown had died, but added: 'I do not believe I was driving dangerously.'

Bett said he had taken cocaine 'on occasions'. The last time before the collision was on November 30, he added.

Asked by Lawrence Bruce, defending, if he had been under the influence of cocaine or its after-effects at the time of the incident, he said: 'No.'

He added: 'I have never experienced a comedown effect.'

The court heard Bett is a director of the family firm Thornham Farms and has been qualified to drive tractors since the age of 16.

His mother and girlfriend were present as the verdict was delivered, but his father, who attended much of the trial, was not in court.

A jury of seven men and four women heard the case after one female juror was discharged midway through.

The judge imposed an interim driving disqualification.