Richard Huckle – dubbed Britain's worst paedophile – thought that using the 'dark web' would conceal his perverse sexual desires for children. The grammar-school pupil turned Sunday School volunteer from Ashford in Kent used the secretive portal to post more than 20,000 sickening images of Malaysian children as young as six months old being sexually abused.

Using a paedophile site entitled Love Zone, he posted a DIY-manual called Paedophiles and Poverty: Child Lover Guide. In it, he said that poor children were "easier" to abuse and detailed steps to remove children's clothes and sexually abuse them as they slept.

The dark web made Huckle immune to capture, allowing him to carry on systematically abusing and raping babies, toddlers and young children while posting horrendous images and descriptions to the forum.

His slew of harrowing crimes may have continued were it not for the tiniest of details: a freckle and the word 'hiyas'.

'Hiyas'

In one of the biggest investigations into sex offenders hiding behind the anonymity of the dark web, Australian police were aware of the Love Zone forum - showing the abuse of babies and very young children.. They discovered its creator used 'hiyas' as a greeting message to other paedophiles, and detectives begun trawling the open internet and legitimate forums for the word.

Eventually, they pinned the word to a Facebook account that proved to be a fake one. However, the trail did not end there. Police searched the details of a car in the account's profile photo and were led to a man called Shannon McCoole, a child care worker in Adelaide, who was working on the site when officers burst through his door.

They knew he was their man because of a distinctive freckle on his hand that also appeared in images of abuse on the forum. Police then assumed his identity and ran the site, which is when they were alerted to Huckle's activities.

He gave away enough information to reveal his identification and that he would be returning to the UK for Christmas in 2014. Upon landing at Gatwick Airport, he was met by officers from the National Crime Agency and arrested.

He now awaits sentencing at the Old Bailey after admitting to 71 counts of sexual abuse – including 14 counts of rape and 31 of sexual assault – committed against against boys and girls aged between six months and 12 years from 2006 to 2014.

He faces life in prison when Judge Peter Rook hands down his sentence on Friday (3 June 2016).