An organization known as Black Death claimed credit for abducting her and were planning to auction her off for 250,000 euros (US$300,000) but one of her kidnappers is understood to have changed his mind when he discovered she had a young child.
A Polish national, Lukasz Herba, 30, has been arrested by Italian police. Herba lived in Birmingham and his flat in the city has been raided by the National Crime Agency, who are working with Italian police.
The 20-year-old model, who is now recovering at home in south London, was seized by two men when she arrived in Milan for a photoshoot on July 11.
She was bundled into a bag and driven for three hours to a house in the village of Borgial, close to the French border and told she was going to be sold on the dark web.
But her kidnappers then contacted her agent and demanded a ransom. He immediately contacted the police, who eventually tracked her down.
"I've been through a terrifying experience. I feared for my life, second by second, minute by minute, hour by hour," said Ms. Ayling.
"I'm incredibly grateful to the Italian and UK authorities for all they have done to secure my safe release," she added.
Up to 80 percent of the internet is said to be hidden in what is known as the dark web, or deep web.
It is a mysterious place which cannot be accessed via traditional search engines. In other words, it is collection of websites that are publicly visible, but hide the IP addresses of the servers that run them.
Drugs and firearms are known to be on sale on the dark web, and it is also widely used by pedophile groups.
But this is the first time it has been linked to sales of adult women. Ms. Ayling said she was told the Black Death group took girls for the "Arab market" and was also told that when those who bought the girls lost interest in them they fed them to tigers.
Dozens of photographs of a scantily clad Ms. Ayling can be seen on her Instagram account and some people have sought to blame her for being kidnapped.
"I think the type of photos you were posting here got you into that trouble. There are many creeps out there using Instagram," wrote Tom A. Anderson.
"The National Crime Agency and the East Midlands Special Operations Unit have been providing support to the Italian authorities during this investigation," said a National Crime Agency spokesperson.
"We collaborate with our international partners in order to make the dark web a less attractive place for criminals to operate, however we do not comment on specific websites or operations," he added.
Ms. Ayling has said she knew there were five kidnappers but she only saw two during her ordeal.
An Italian lawyer representing Ms. Ayling said she had been through a terrible ordeal.
"It must have been terrible for her, a terrible human experience," said Francesco Pesce.
He said Ms. Ayling had taken the police back to the cottage where she was held, which he described as a "hideous place."
"Prosecutors are now concentrated on finding accomplices… as this whole story is linked to a wider, darker picture," said Mr. Pesce's mother, Daria.