A crime clan member turned supergrass who was vital in the conviction of Christopher Hughes also helped snare another killer.
The informant was quizzed for several days in the trial of gangster Hughes at the High Court in Glasgow.
Hughes has been told he will spend at least 25 years behind bars after being convicted of murdering Dutch criminal-turned-blogger Martin Kok.
But the inside man that helped to snare Hughes had testified just weeks earlier in the case of Jordan Owens, 27, at the same court.
Owens was later jailed for a minimum 23 years for the murder of new dad Jamie Lee, who was gunned down in Glasgow's Castlemilk in 2017.
The informer told jurors how Owens and Hughes both confessed to him as they were fugitives in the Belgian city of Antwerp.
His crucial role in both trials can only now be revealed after a reporting ban until the end of the Hughes case.
The witness - who cannot be identified - met Owens in an Antwerp flat in November 2017.
Owens had arrived there effectively in the back of a lorry after being ferried away to Europe by criminal associates.
The supergrass said: “It was in a compartment built into the lorry for concealment.”
The informer said Owens went on to confess involvement in the shooting of Jamie Lee, 23, at the meeting in the Belgian city.
Owens spoke of “ill feeling” between him and the Lee family.
The informant: “Jordan had got warned that Jamie Lee and his group were coming down to go through his gran’s door.”
Owens said a knife had been hurled at him near a play park shortly before the killing.
A fight then erupted between the groups.
The informer said he was told Owens and a friend raced into a close.
The witness: “He said his friend held the door and Jordan got the ‘tool’ - think he was referring to the gun.
“He opened the door and shot Jamie.”
Prosecutor Lindsey Dalziel: “He told you he shot Jamie Lee?”
The supergrass: “That is correct. In the re-enactment he was displaying he made reference that it was one shot.
“He did not say how far away Jamie Lee was.
“He said that he was dead.”
Miss Dalziel asked: “When he told you this, did he express any emotion?”
The man replied: “No.”
Owens, the informer said, then “fired some shots” at Jamie’s father Joseph until the gun “jammed”.
He then hurled the weapon away and escaped through a fence.
Owens had denied murder.
The witness - who accepted being paid in his role as an informant - later went on to give evidence in the Hughes trial, again from a remote location.
Hughes has been sentenced to at least 25 years in prison after being convicted of luring Dutch blogger Martin Kok to his death on December 8 2016.
The killing was originally due to happen outside the Citizen M Hotel in the Dutch capital of Amsterdam.
But, Hughes, originally from Glasgow, later told the informant that the gun had "jammed" during a "play by play" of events at his flat in Antwerp 11 months later.
The murder then did happen later that night as Hughes paid for Kok's evening at the Boccaccio sex club and supplied him with cocaine.
The supergrass stated that he was speaking to his crime boss on the night of the incident.
The informant said: "He [The boss] had been on about someone waiting for Martin Kok and Christopher Hughes was to hold back.
"Martin left just ahead of Chris and he made a comment about a cat appearing at the club and that he stepped back to pet it."
Prosecutor Liam Ewing QC asked what the significance of petting the cat was.
The witness replied: "Martin was going to his car first so there was no mistake of anyone being caught in the crossfire."
Jurors watched CCTV of Hughes moments after the shooting walking away from the scene texting on a mobile phone.
Mr Ewing also asked the informer if Hughes understood something was to happen to Kok that night.
He replied: "I remember a comment being made about putting him [Kok] on a plate for the Roccies."
The witness claimed he had a meeting with his boss a month after the murder.
He said: "I was told it was an arrangement because the lad had access to Martin with a group called the Roccies, a Moroccan crime group, who are all over but more prominent in Amsterdam."
Hughes' boss then organised for him to be picked up as he hid in bushes while mercy crews arrived at the scene.
Hughes told police the next day that he was involved in "tech support" with the phone company - which was funded by £1m in dirty money - but did not want to give names of who was involved.
He further stated that he binned his encrypted phone as it had smashed and got rid of his clothes.
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