He denied burgling the Alan Berry Building at Coventry University, and on the day of his trial it was agreed not to proceed with that charge and to leave it on the court file.
Prosecutor Raj Punia said that in March 2007 Arnold had pleaded guilty at the court to wounding Jason Backes, the caretaker at King Edward VI School in Stratford, with intent to resist lawful detention and two charges of theft.
He was given an indeterminate prison sentence for the protection of the public, with an order that he should serve a minimum of two years before he could be considered for parole.
Although he was still serving that sentence in June this year, after a succession of parole applications had been rejected, he was in HMP Ford open prison in West Sussex.
And when a role call was carried out at 8.30 in the evening on 20th June Arnold, who had last been noticed at 5pm, was not there, having simply walked out of the unlocked gates.
He was arrested on 9th July after security staff at the Alan Berry Building in Priory Street, Coventry became suspicious about him being there and challenged him.
They then called the police and Arnold, who gave a false name, was arrested on suspicion of burglary.
He was put into a police car where one of the officers saw him take something from his waistband—and in the car the officer found a kitchen knife with a three-inch blade.
When Arnold, who said he had taken cocaine and heroin, was later interviewed he said he had travelled from Birmingham to Coventry and just happened to be looking round the building.
He denied he was intending to steal anything, and said he had the knife on him to self-harm, said Miss Punia.
The court heard that Arnold’s original sentence had been imposed after he had stolen two handbags belonging to members of staff at a shop in Stratford town centre.
He took them to King Edward VI School in nearby Church Street where Mr Backes found him hiding in the toilets as he searched the two bags.
Mr Backes and the school’s assistant head restrained him and took him to the medical room to wait for the police.
But Arnold grabbed a pair of scissors from the medical box in the room and lunged at Mr Backes before running from the room, chased by the caretaker and the assistant head.
When they caught him Arnold struggled and stabbed Mr Backes to the cheek near his jaw, causing a deep wound, and ran off into the town centre.
But he was caught after two pupils who had seen him at the school saw him on a train on their way home and called the police who stopped it at Earlswood station and arrested him.
Daniel Oscroft, defending, accepted the sentences for escaping and having the knife would have to be consecutive.
But he pointed out that will not affect the time Arnold still has to spend in jail anyway under the indeterminate sentence which he is still serving, and from which there was no hope of release for the foreseeable future.
Mr Oscroft said Arnold had been biding his time in jail until the Parole Board considered him eligible for release, but he had given up hope and was desperate to see his children.
Judge Sylvia de Bertodano told Arnold: “I am not without sympathy for you, believe me.
“I can understand how you became overwhelmed by a desire to see your children and that caused you to walk out of the door. You say it was worth it to see your children, but it’s unfortunate you have put your overall position back in this way.
“Escape must always be a consecutive sentence; but it is clear this was not part of some big plan. You just walked out, and you were at large for some three weeks.
“I very much hope that, having seen your children, you can put your head down and continue with what you’ve been doing in prison and work towards getting your permanent release at your next Parole Board hearing.”