The junkie lifer scored legal highs Spice and Black Mamba worth thousands of pounds from dealers in Hatfield open prison in Doncaster, South Yorkshire.
He promised to pay for the drugs with cash gathered during a home visit after the death of his mum, who he had not seen for ten years.
The cheeky con even borrowed a £4,000 watch and designer Gucci bag before being granted the time out by bosses at the Category D nick.
But instead of returning to Hatfield he handed himself in at HMP Pentonville in London. Last night prison chiefs were investigating how an inmate jailed for murder with a history of drug abuse was allowed to trek across the country unchecked.
The Londoner, who was 15 years into his life sentence, was being quizzed by red-faced bosses.
Insiders told the Daily Star Sunday the inmate set up deals for legal highs, vowing to pay for them on his return from home leave.
He also promised fellow druggies he would bring back legal highs if they “pay half now, half later” – but had no intention of bringing back “the parcels”.
The source said: “He was touting for business days before he left and he even conned one prisoner into lending him his four grand Breitling watch and a Gucci manbag.
“He said he was going to see his family after his mother died and the governor – whose offices he regularly cleaned – granted the leave.
“He left promising to bring back cash and a load of Spice for other inmates.
“Obviously he had other ideas and ended up doing neither.”
Our source added: “By the time he turned up at Pentonville 200 miles away he had done everyone up like a kipper.
“But he will probably repay his debts one way or another.”
Spice, Black Mamba and other legal highs are rife in Hatfield and other jails across the UK.