A police officer had his leg amputated after being hit by a driver who fell asleep at the wheel, a court has heard.

Ewan Simpson was heading home from work on his motorbike when Alan Tait's Volvo smashed into him on the A952 near Mintlaw, Aberdeenshire, around midnight on October 2015.

Tait then left the badly injured officer for dead in a dark field as he fled the scene without calling for help.

The 36-year-old has been remanded in custody after he pled guilty to a charge of causing serious injury by dangerous driving.

Mr Simpson, who was 32 at the time, was heading home from his shift at Fraserburgh police station when he spotted Tait's car veering into his path.

Prosecutor Lynsey Rodger told the High Court in Glasgow: "Tait did not brake and did not make any attempt to avoid colliding."

The court heard his car ploughed into Mr Simpson, crushing his right leg. The officer was thrown into the air, hitting the ground several times before ending up in a field.

Tait eventually came to a stop in a ditch. As Mr Simpson yelled in pain, Tait got out and asked if he was hurt before walking off, claiming he would have to get help.

Another motorist was driving on the same road when he spotted Tait's car and pulled over.

Tait, described by the driver as “worked up and wired” asked for a lift to Fraserburgh. He told the motorist no one else had been involved in the crash.

Meanwhile, Mr Simpson managed to drag himself a short distance across the field before getting caught on barbed wire.

He then unsuccessfully attempted to hurl his bike helmet on to the road to attract attention. As the officer began to fear for his life, he tried to stem the flow of blood by tying his belt around his leg.

Ms Rodger told the court: “He screamed and screamed for help. A number of cars passed but none stopped. He thought he was going to die.”

At 12.50am, two nurses were driving past when they saw Tait's car still in the field. They got out and found Mr Simpson, administering first aid before an ambulance arrived.

The court heard Ewan suffered multiple fractures to his right foot, ankle and lower leg.

The advocate depute said: "The leg could not be saved and, later that day, it was amputated below the knee."

Mr Simpson also had fractures to his right arm, which needed bone grafts and a metal plate inserted. He was in hospital for almost two months before finally being released.

The court was told Tait finally phoned police hours after the crash but said no one else was involved.

He was held by officers later that morning and asked: "Is this because of my silver Volvo?"

Tait admitted five other charges including culpable and reckless conduct by failing to get help for Mr Simpson.

Judge Lord Bannatyne deferred sentencing for reports until April 11 in Lanark.