A former Norfolk policeman who stole 10 ancient gold coins he found with a metal detector has been jailed.

David Cockle, 50, found the Merovingian Tremissis coins in a field in west Norfolk and sold them to a dealer for £15,000.

He had entered into a contract with the landowner to split the proceeds of any find, but failed to tell the landowner of his discovery.

He also failed to tell the coroner, instead selling the coins in three smaller batches to disguise the fact they were treasure trove.

Another metal detectorist had discovered 35 Merovingian coins at the same site and declared them honestly.

Had Cockle done the same, the discovery would have been the largest find of Merovingian coins in the UK.

Cockle, formerly of Stoke Road, Wereham, Norfolk and now of Carroll Close, Leigh, Greater Manchester, admitted theft at an earlier hearing. Three counts of converting criminal property will lie on file.

Judge Rupert Overbury, sentencing at Ipswich Crown Court, said Cockle had more than 30 years of experience as a metal detectorist and knew the legal process he should have followed to declare the find.

He told Cockle: 'The motivation for your dishonest behaviour was pure greed.'

Cockle was jailed for 16 months and banned from metal detecting for five years.

Under the five-year criminal behaviour order, he is also banned from owning metal detecting equipment and from entering into agreements with landowners to use their land for metal detecting.

Cockle was dismissed from Norfolk Police for gross misconduct in February as a result of his actions.

Senior district crown prosecutor Punam Malhan said: 'David Cockle had permission from a Norfolk landowner to use a metal detector with an agreement that anything he found he would report and surrender.

'He found 10 Merovingian Tremissis gold coins from Gaul dating back to the sixth or seventh centuries. Such finds are extremely rare in this country and to find them was a significant discovery. A similar find in the same location by a different person was reported and declared treasure trove.

'No matter how excited someone might be at finding buried gold treasure, there is a proper procedure to be followed when that happens. This is so that the find is correctly assessed and the historical importance of the find and its site recorded for future generations.'

'We take heritage crime seriously as it harms the value of our country's heritage assets for ours and future generations. Where a discovery is not recovered, it is felt not just by the owner but by the community as a whole as it cannot be replaced.'

Nick Bonehill, mitigating, said Cockle was of previous good character, had a successful career in finance before he joined the police and could no longer work in either sector as a result of the dishonesty conviction.

Cockle had split from his wife, who also worked for Norfolk Police, in 2012.

The court heard he was motivated by his ex-wife's demands for a £10,000 divorce settlement, but Judge Overbury noted that Cockle had also suffered gambling losses.

The coin dealer, who had bought the items in good faith, was left out of pocket by Cockle's actions.

A proceeds of crime hearing will take place at a later date.