A prolific and “evil” child rapist has been jailed for life after being unmasked using new technology developed in the UK that unpixelated an image of his face found in photos he had taken of himself abusing his victims.

Martyn Armstrong, from Pembrokeshire, documented himself committing “depraved” acts against three children, including a victim as young as one, over a number of years and posted the pictures to the dark web.

The 50-year-old was arrested in July last year after officers developed the never before used tool.

He pleaded guilty to a total of 41 counts of rape of a child under the age of 13 and sexual assault related to two victims, and to making, distributing and possessing indecent images of children in relation to them both and a third victim.

Roger Griffiths, prosecuting, told Cardiff Crown Court Armstrong had taken the images of him abusing children between 2005 and 2007, and between December 16, 2009, and February 6, 2011, and had admitted to taking photos of a third child on a beach in 2010.

Armstrong had posted online a series of 200 extremely graphic images and a video under the file name ‘Father Jones’ which shows him repeatedly raping his youngest victim.

The series has been known to crime agencies across the world since 2013 due to the file being shared and downloaded across 18 countries, not including the UK, within South America, Australia and Europe.

The folder was still being shared in the UK in early 2022 across six websites, and had been found by police forces in 583 forensic submissions.

Mr Griffiths said Armstrong had used photoshop to place a zig-zag distortion across his image, but made no attempt to disguise the identities of his victims.

Due to his face being blurred, investigators were unable to identify the paedophile for almost a decade, despite attempts by law enforcement partners from Australia, Italy and France, with an officer from the latter country identifying the exact beach location in Wales which had featured in some of the images.

Mr Griffiths said: “One image featured the offenders face with a zig zag distortion.

“As a result in July 2022 and the National Crime Agency officers using their new tool they were able to unpixelate the image of the defendant in that series.”

The software was developed by NCA officers in the UK and is the first of its kind to be developed in the world.

It is expected the programme will help future perpetrators to be identified.

From the undistorted image, the officers were able to identify Armstrong’s Facebook profile leading to his arrest.

Officers seized a number of his devices and discovered a disturbing cache of images including 789 category A, 989 category B and 2227 category C.

Mr Griffiths said: “Mr Armstrong was tracked down and asked if he was guilty of the offences and he answered ‘to some of them yes’.

Armstrong admitted to distributing photos and to naming the Father Jones series, saying he had also taken images of one of his victims on a beach, telling officers: “I always have a camera with me.”

Adam Sharp, defending, said: “Mr Armstrong does not want me to try to mitigate the depravity of his actions or the impact they had on his victims.”

Mr Sharp said his client has taken full responsibility for his actions, but asked the judge to take into account how he cooperated with officers and had led them to identify other victims.

In a victim impact statement read to the court, one of his victims said: “The second I saw the piece of paper (with the images), it felt like I couldn’t breathe.

“I saw my smiley, younger self full of happiness, confidence and innocence.

“I am no longer able to look at these pictures without a rush of panic and heartache.

“I feel betrayed, manipulated and deceived.”

Addressing Armstrong, they said: “You abused me, manipulated me and have forever darkened a piece of my childhood.

“When I think about the type of person who could commit such horrific crimes, I feel like only a monster could ever be responsible. Never did I think that all along, the only monster was you.”

Sentencing Armstrong to a life imprisonment with a minimum term of 14 years, Recorder of Cardiff Tracey Lloyd-Clarke said: “In these courts we deal with the most serious sexual offences but the nature and depravity of your offending is shocking.

“No doubt you thought the precautions you took to hide your identity would protect you from being identified.

“Thanks to the good work of officers from the National Crime Agency and other law enforcement agencies across the world you were apprehended.”

The judge said probation officers had categorised Armstrong as high-risk and found he had an “obsession with the sexual abuse of children and babies”.

“You distributed images of children for the sexual gratification of other paedophiles,” she added.

“That will continue for the rest of their lives because these photographs cannot be recalled.”

Armstrong was also made the subject of a 25-year sexual harm prevention order, along with restraining order in relation to the three victims.

Wearing a navy blue fleece and blue polo shirt, he showed no emotion as he was taken down.

Martin Ludlow from the NCA said: “It is over 17 years since Armstrong began to abuse these young children. I don’t believe he thought he would ever be caught and that the distortion techniques he used would protect him.

“However, the NCA and our international partners were determined to ensure his evil actions did not go unpunished.

“Our commitment to identifying him was unwavering and ultimately, NCA officers developed a completely new programme which led to his unmasking.

“We will continue to work together and do all we can to bring offenders like Armstrong to justice and protect innocent children from child sexual abuse.”