A driver who killed two young women after collapsing at the wheel will not face a trial.

William Payne ran over 18-old Mhairi Convy and 20-year-old Laura Stewart on a Glasgow pedestrian crossing in 2010.

The 54-year-old, from Bishopbriggs, had suffered six blackouts in the three years before the crash.

Last year a Fatal Accident Inquiry (FAI) found Mr Payne - or his doctors - could have helped avoid the tragedy by telling the DVLA about his health problems.

However, Crown Counsel, some of the most senior lawyers at the Crown Office, have decided not to prosecute Mr Payne. They do not believe they believe they could prove criminal negligence on his behalf.

A Crown Office spokesman said: "In order to bring a criminal prosecution, the Crown would need to prove that the driver knew that to drive on the day of the incident was to do so in the face of a known and obvious danger - that he was liable to lose consciousness while driving that morning.

"Following consideration of all the evidence Crown Counsel has concluded that the Crown cannot prove this and as a result has instructed no proceedings."

After the crash Mr Payne was initially charged with causing death while driving without insurance but this charge was dropped.

The families of the two victims - who were told about the Crown decision last week - are deeply unhappy.

Linda Stewart, Laura's mother, said: "Our chief question will be 'Why did it take so long to reach this decision?'

"We were told there was to be a review in March last year after the FAI and it has taken another year to come to the same decision.

"When we met Crown Counsel previously, the official said they could not prosecute on a whim. Well, this is not done for us. We are not going to go away."

Prosecutors said they recognised their decision would be "disappointing and upsetting to the families of the girls".

A spokesman: "However, this is a legal decision and was inevitable following the insufficiency of evidence."

The Crown is responsible for both calling FAIs and prosecuting driving offences. The investigation was led by a specialist unit of prosecutors who deal with serious road traffic accidents.