Two British men - one a former serviceman - are being held in a high-security Norwegian prison accused of money laundering after a job transporting £1.5million of silver coins seemingly went wrong.

Dad-of-one Samuel Cook, 31, and another man, yet to be named, work as close protection officers for a UK-based company, and usually deliver goods or protect high-profile individuals.

But last month they were hired, via their company, to move a consignment of 500kg of silver coins between two locations in Oslo, Samuel's family say.

The pair were on their way to drop off the package when they were stopped by police in Oslo and arrested on suspicion of aggravated robbery, according to Samuel's dad, Steve Cook, 54.

A month on, Samuel, from Exeter, Devon, and his companion, understood to be a former Royal Marine, remain in high-security Ringerike Prison - famous for housing mass murderer Anders Breivik.

On May 22, Police successfully appealed to keep them detained for a month longer, Steve said.

He says the pair have no idea why they have been held, and thought it was a simple, straightforward job to transport goods.

Samuel's solicitor, Odd Martin Helleland confirmed Samuel has been charged with negligent money laundering.

Mr Helleland confirmed that Oslo District Court felt there was "reasonable ground for suspicion" and detained him a further four weeks.

Steve and wife Sarah Cook, 50, are "distraught with worry" over their son.

Steve, a Royal Marine from Exeter, Devon, said: "I got a phone call four weeks ago saying they have been stopped by police.

"As far as Samuel and his co-worker were concerned, it was all legal, and above board.

"The role is to do secure deliveries and escorting people but you don't really know your mission until you arrive.

"They were hired as couriers in good faith.

"We don't think they've been charged but it's been a month and they haven't been released.

"Apparently they were first arrested for aggravated burglary.

"They were getting £250 a day, for three days.

"Who would risk prison for £750?"

The pair were hired on April 21 by a company who contracted their workplace, and their transport and accommodation was arranged for them, Steve says.

They flew out to Oslo from Heathrow soon after, and were arrested on 22nd April.

Steve said the British Embassy this week informed him the reason for their detention is now considered alleged "negligent money laundering" rather than robbery.

The pair appeared at a hearing on Thursday (22) at Oslo District Court with solicitors and were told they would be detained for another month.

Translated Oslo District Court documentation claims it was deemed highly probable that the silver coins were proceeds of illegal activity.

The Court of Appeal argued the circumstances suggest that Samuel and his colleague "most likely understood" that the coins may have been obtained through criminal offences.

But Steve said Samuel - who is registered disabled due to having bipolar disorder, ADHD and depression - has no criminal record, and would not knowingly commit a crime.

It is understood the two men were not known to each other before taking on the assignment.

His family have spoken to Samuel a handful of times since he was detained and he seemed ok, but was lacking sleep.

A FCDO (Foreign Office) Spokesperson said: “We are supporting two British men detained in Norway and are in contact with the local authorities”.

The Norwegian Correctional Service said it is "prohibited by law from disclosing information about individual inmates".

A spokesperson for Oslo Politidistrikt - the Oslo police - said: "This case has been transferred to the National Authority for Investigation and Prosecution of Economic and Environmental Crime (Økokrim)."

State prosecutor Jon André Hvoslef-Eide, of Økokrim said: "We can confirm that the arrests are linked to an investigation in Norway.

"The investigation is ongoing, and we therefore have no further comments."