WATCH: Royal Marines reservist jailed for 14 years over stolen arms cache

Martin Shannon, 43, of Hythe, Southampton, took guns, ammunition, explosives and grenades from his base in Poole over four years and buried them in the New Forest.

He was snared by an undercover National Crime Agency officer who handed him £10,000 for the sale or loan of items including ammunition and guns at a meeting in a pub car park near Newbury.

Following his arrest, Shannon told officers he wanted to make money selling the guns to 'Great Train Robber types' who would open safes in a 'cloak and dagger' style before 'running off into the sunset'.

The defendant, who described himself as a 'broken man', was suffering from post-traumatic stress disorder after serving in Iraq and Afghanistan.

He pleaded guilty to 15 various firearms offences at the Old Bailey.

He admitted taking a C8 automatic assault rifle and a semi-automatic Sig sauer P226 handgun from RM Poole in Dorset, as well as thousands of rounds of ammunition and a number of high-explosive hand grenades.

In September , he met an undercover officer who was posing as someone interested in buying them.

They met in the Chieveley area of Newbury in Berkshire and, after some discussion, Shannon supplied the assault rifle, the handgun, 9mm and 5.56mm ammunition for both guns, a sawn-off shotgun, grenades and pyrotechnic munitions to the officer for £10,000.

Shannon then made his way home unaware he was being followed by surveillance officers from the NCA’s Armed Operations Unit.

He stopped off at a supermarket in Winnall, Winchester and was arrested as he came out.

During his interview, Shannon admitted he had buried another shotgun. He was taken to the spot where he thought the weapon was but could not locate it

Officers conducted a more thorough search and the weapon – a bolt-action shotgun - was recovered.

Sentencing, Judge Richard Marks QC highlighted the 'breach of trust' of Shannon as a serving Royal Marine reservist.

The fact that once he had handed the guns into criminal hands he would have no control over them was also a serious feature of the case, he said.

Judge Marks accepted that while on active duty in Iraq and Afghanistan, Shannon had suffered from PTSD which affected him 'particularly badly'.

It caused his thought processes to become 'illogical' and saw him spiral into alcoholism, he said.

The judge said: 'This is a tragic case, in particular for you and your young family.'

Shannon held up a closed fist and smiled at supporters in the public gallery as he was sent down to begin his jail sentence.

In mitigation, Kevin Hall said the defendant had 'endured traumatic events beyond most people's comprehension'.

Shannon's PTSD was triggered by his experiences serving in Iraq in 2003 and Afghanistan in 2006 and was compounded by the deaths of two close friends and colleagues in 2010 and 2014.

The family man now described himself as a 'broken man' who was desperate for treatment, the lawyer said.

Shannon had joined as a Royal Marine reservist in 1996 and was also a commercial diver and HG driver.

Earlier, the court had heard how the Ministry of Defence (MoD) launched an inquiry after supplies went missing from the Poole base.

Mark Webster, director of Intelligence and Operations at the National Crime Agency said: 'This has been a complex investigation into an individual who had access to and possession of extremely dangerous weapons.

'We worked closely with the Ministry of Defence, who embedded staff into our operational team to provide invaluable information, advice and guidance about the weapons and also the training RM reservists receive.

'This allowed us to more accurately assess the threat Shannon posed and put in place plans to arrest him safely.

'We don’t believe Martin Shannon was working as part of an organised crime group, but I want to reassure the public that where people have access to firearms and intend to use them for criminal activities, we will work with our partners to ensure they are stopped and held accountable for their actions.'

Details of the weapons and ammunition seized:

1x automatic assault rifle (C8)

1x semi-automatic Sig sauer handgun (P226)

1x Shortened (or ‘sawn-off’) shotgun (.410 El Faisan)

1x Bolt-action shotgun (Mossberg 395KB 102)

Magazines containing ammunition (unverified amount)

1,400 rounds of 9mm ammunition

275 rounds of 5.56mm ammunition

118 shotgun cartridges

7x High Explosive Grenades

3 x 3x6 flashbangs

2x smoke grenades

8x thunderflashes

2x day and night distress signals

1x detonator with safety fuse

Seized from house

Brown box containing 5.56 rounds

Grey clip with 10 x 5.56mm rounds

Bandolier containing approx. 150 x 5.56mm rounds

Used .338mm casing

1x bullet

Kenco coffee jar containing empty sig sauer magazine and assortment of 9mm ammunition

Two small white boxes containing .338 rounds and 5 loose .338 rounds

Metal tin containing approx. 5 inch block of plastic explosive

1x black inert grenade

1x blue coloured grenade type device

1x green signal kit pyrotechnic pistol 16mm (military)

Pack of ten mini flares