The former agent of a model kidnapped in Italy, said checks on the person who made the booking were carried out.
Chloe Ayling, 20, who worked for Supermodel UK, based in Gainsborough, Lincolnshire, was held near Turin for five days before being released.
She had flown to Italy for a photo shoot on 11 July and the following day her then agent, Philip Green, received a ransom email.
Mr Green said he had no suspicions about the man who made the booking.
"We would not expose anyone to a situation without fully knowing who the client was," he said.
"Every check was done with nothing being flagged up for me to think or even suggest there was anything suspicious about him."
Mr Green said an email was the first he knew Miss Ayling had been taken.
"It was not until just after 10:00 on 12 July, the day after the shoot, I opened my email inbox and found something incredibly sinister and worrying.
"It was the first email contact from someone on behalf of the Black Death group telling me chillingly they had taken Chloe."
He said he was told to find ransom money and if he did not pay they would put her up for auction.
A few days later Miss Ayling was released and eventually returned to the UK on 7 August after speaking with Italian investigators.
Mr Green said he knew many doubted the story initially but his former client had not wanted the case to be made public.
"She said to me 'I don't want this going public, I am actually humiliated by it'.
"It is only now that people are starting to believe she actually went through this."
Investigations into the case are being carried out by authorities in Italy, Poland and the UK.
Polish national Lukasz Herba, who lives in Oldbury in the West Midlands, has been arrested on kidnapping charges.