Devon McCallum, 28, and 27-year-old Nardia Seedat were traced after police found £1,500 cash and a mobile phone when they searched the boy at Rochester railway station in Kent in September 2020.
Suspecting he was being exploited by county lines dealers, officers referred him into the national referral mechanism for safeguarding and launched an investigation into his controllers.
Data downloaded from the phone showed multiple calls and texts from a contact saved as “SYK” and a text from another number directing the boy to take the 4.55pm train from Deptford in south east London to Rochester on the day of his arrest.
Information from cell sites found the two numbers were in constant contact with the 13-year-old’s phone throughout the previous month as he travelled between London and Kent.
British Transport Police (BTP) detectives were able to link McCallum – also known as “Sykes” – to the “SYK” number and the second number to Seedat.
As the boy traveled between London and Kent, broadcast messages were being sent from the “REM” county line, controlled by McCallum, to contacts in Medway.
The messages offered heroin and crack cocaine for sale and read: “back on got both – REM”.
Cell site data of the phone numbers revealed McCallum and Seedat were staying at an address in Surrey Quays, southeast London.
At the time McCallum was on an electronic tag curfew, requiring him to be at the address between the hours of 9pm and 7am.
A warrant was executed at the property on the morning of 25 September, 2020, where McCallum and Seedat were discovered asleep on two sofas that had been pushed together to form a bed.
Three mobile phones, including the two handsets used to contact the boy, were seized from the address and the pair were arrested.
When Seedat was searched officers found she had concealed 14 wraps of heroin and a wrap of crack cocaine.
McCallum attempted to distance himself from the Surrey Quays address when interviewed by claiming a friend let him stay there and that “lots of people come and go”.
Seedat responded “no comment” to all questions put to her in interview, but just before its conclusion stated: “I’m not involved in trafficking”.
McCallum pleaded not guilty to conspiracy to supplying heroin and crack cocaine.
Seedat denied conspiracy to supply heroin and crack cocaine and two counts of possession of class A drugs with intent to supply.
Both were found guilty of all charges following a two-week trial at Inner London Crown Court earlier this year.
McCallum was jailed for nine years and Seedat to three years and six months, when they were sentenced at the same court on Friday, 21 October.
Detective Superintendent Gareth Williams, of BTP’s county lines taskforce, said: “Sadly, it is not uncommon for drug suppliers to use children to transport drugs on the railway.
“The 13-year-old boy my team successfully safeguarded is the youngest we’ve encountered being exploited – we routinely come across teenagers in our work.
“McCallum and Seedat are a callous pair of criminals who controlled a child for their own financial gain.
“I hope their adequately strong sentences serve as a stark warning to offenders – we will catch you and put you behind bars.”
He added: “If you spot the signs of child exploitation on the railway network, I urge you to report it to us by texting 61016 or calling 0800 40 50 40. No report is too small or too trivial.”