An inmate dismantled his cell TV and fashioned the parts into blade-like weapons that he strapped to his hands.
Safe cracker Ovidiu Dinu, 32, serving a two-year-and-eight-month term at HMP Grampian, had "struggled to adjust" to life behind bars, a court heard.
He bound two 25cm-long pieces of metal debris to his hands with cloth as makeshift weapons, Peterhead Sheriff Court heard (Monday 12 July) as he appeared via videolink.
His defence agent said he was frustrated and had acted in a threatening manner but had no intention of harming anyone.
Dinu admitted possessing an offensive weapon in prison last October as he was awaiting sentencing for his crimes. He was admonished.
He was locked up for breaking into premises through shop roofs and cutting open safes in a series of daring heists across Scotland.
Fiscal depute Brian Young told Peterhead Sheriff Court the "makeshift weapon" measured 25cm in length.
He said: "The accused was the sole prisoner within his cell when at around 10.30am he armed himself with two long pieces of metal debris from a television.
"He bound these to his hands with cloth to make improvised weapons. They measured 25cm in length."
When prison guards caught wind of the situation they went to his cell where he allowed them in to remove the wires from his hands before he was shipped to spend a week in segregation as punishment.
Dinu's defence agent Caitlin Pirie said her client hadn't been coping well with jail and the isolation had hit him hard.
"He was finding his period of remand extremely difficult," she said. "He was struggling with his mental health and not in a great state of mind.
"He was extremely frustrated that day. He had damaged the television and although he was armed he had no intention of harming anyone. But he does accept he was acting in a threatening manner."
She added he was "deeply sorry" and had prepared himself for an additional period in custody as a result of the incident.
Dinu was sentenced to two years and eight months behind bars last month.
He and Gabriel Fratila carried out the audacious crimes by breaking in through shop roofs and cutting open safes.
On one Mission Impossible-style raid the pair lowered themselves into a Forres garden centre before making off with cheque books.
They hit retail businesses in Elgin, Forres, Edinburgh and Glenrothes in 2020 - making off with thousands of pounds and causing tens of thousands of pounds of damage to buildings.
The two men were caught when DNA evidence linked them to a bottle of Coca-Cola left at the scene of one of their break-ins.
Dinu broke into the Mackenzie and Cruickshank Garden Centre in Forres, where a number of charity tins were nicked. He also targeted a commercial premises in Elgin which netted more than £1,000.
He was apprehended by police while disembarking from a ferry at Port of Holyhead in Wales in September 2020.
Miss Pirie said Dinu had come to the UK from Romania to "seek a better life" after a number of false starts.
She claimed the father-of-one had hoped to find work here when he made the move in August last year, but was "drawn into criminal behaviour" instead.
Sheriff David Mackie told him: "I take into account of the fact that at the time of this offence your mental state was poor and when you were asked to calm down, you then did so.
"In the end, it boils down to you having caused damage to your cell. There's no suggestion in the account that has been given to me you showed aggression to the officers or had any contemplation of harming anyone but yourself."
Ovidiu Dinu is serving time in HMP Grampian for breaking into premises through shop roofs and cutting open safes.
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