A grandson stabbed his frail grandmother in the arm during a violent family argument about his problem drinking.

Gary Nightingale grabbed a knife and lashed out when he was confronted by his mother and grandmother, who had found him drunk at her home.

He caused a small wound in his grandmother's arm and struggled with his own mother before they used an emergency alarm to call the police.

When it was answered, he shouted that it was a test but the operator could hear screams of terror in the background and realised an attack was under way, Exeter Crown Court was told.

Nightingale, 46, of Hynetown, Strete, admitted causing actual bodily harm to 86-year-old Vera Osborne and common assault on his mother Linda Nightingale.

He was jailed for 12 months, suspended for 18 months, and ordered to do 40 hours unpaid community work and receive supervision for a year. He was also banned from going to his granny's home in Bidders Walk, Stoke Fleming, for two years.

Recorder Mr Ignatius Hughes told him: 'You got drunk and got violent and you terrified both your mother and grandmother.

'Your mother survived unscathed but witnessed you stabbing your grandmother in the arm.

'Fortunately for her, you did not cause serious injury but this was an attack in her own home by someone she should have been able to trust.'

 The judge said he was able to suspend the sentence because of the determination Nightingale is now showing to tackle his alcohol problem.

Janice Eagles, prosecuting, said Nightingale was a regular visitor to his grandmother's home and helped look after her on occasions. She was elderly and suffered from Alzheimer's.

On the day of the attack last month his mother and grandmother returned from a day out to find he had let himself into the house and was in a drunken stupor on a bed with a half finished bottle of vodka. His mother poured it away and when he woke up he became angry and picked up a knife.

Miss Eagles said: 'He threatened to kill them and could be heard on the emergency call tape blaming his mother for his problems. Both women were extremely frightened and at one point the grandmother can be heard screaming.

'He pulled the landline out of the phone to stop them calling for help and his grandmother used her alarm to summon assistance. Initially he shouted that it was a test but his mother said it wasn't and it became clear they needed help.'

Anne Bellchambers, defending, said: 'This must have been a terrifying incident but his sister is willing to give him a home and says that when he is not drunk he would not hurt a fly.'