A paedophile is facing the rest of his life in jail after admitting 45 sex offences against children in Britain and abroad amid fears the full extent of his abuse could be far worse.
Retired English teacher Mark Frost, formerly known as Andrew Tracey, 70, pleaded guilty at the Old Bailey to a catalogue of abuse against nine children in Thailand between 2009 and 2012.
Frost raped impoverished Asian boys and encouraged them to engage in sex acts after he groomed them with cash, sweets, computer games and swims in his pool.
He skipped bail to avoid prosecution in Thailand but was extradited from Spain last year after his activities were uncovered by Dutch police on the computer of a man in the Netherlands.
Frost got the boys aged between 10 and 14 to give thumbs-up signs and make love heart gestures with their hands while being filmed on a webcam engaging in sexual acts.
The Dutchman they knew as Simon watched the abuse online and made suggestions for what they should do to each other from afar, the court heard.
Frost admitted a raft of charges including multiple rapes, sex assaults, inciting children to engage in sexual activity and making indecent pictures.
Since the allegations emerged in Asia, two former pupils of a school in Worcestershire have come forward claiming they were sexually assaulted in the 1990s. One of them has since died.
Frost had sex with his late victim in a school store room, during breaks, and at his home where he lived with his adopted son.
In a statement read in court, he said his life had been blighted by what happened and he lived in "constant fear" the video Frost made of him would come out.
The other vulnerable victim said he had sex at Frost's home, in a barn and during a camping holiday in Wales and was left "scared and embarrassed".
The now-grown man told police that he was rewarded with cigarettes, money and "nice things" and had decided to come forward now to stop Frost abusing anyone else.
The National Crime Agency believes Frost may have assaulted many more youngsters he had contact with through his 25-year career in schools in east London, Hertfordshire and Worcestershire and as a senior Scouts volunteer.
He was brought to justice through a complex international investigation involving the NCA and authorities in Thailand, the Netherlands and Spain.
In 1978, he subscribed to the Paedophile Information Exchange (PIE), an international organisation of people who traded obscene material.
In 1986, the unmarried teacher tried to adopt a son through the Catholic Church and was turned down, only to succeed through a local authority, the NCA said. The pair are now estranged.
In 1992, he was fined for possessing indecent photographs of a child and the following year was jailed for a year for allowing his premises to be used for drugs and sex with an under-age girl.
Three years later he was banned from teaching by the Department for Education.
In 1998, he was jailed for a year for indecent assault on a male under 16 and put on the sex offenders register for 10 years.
Once he was taken off the register, he moved to Thailand where he groomed children for sex and threatened them with violence if they told anyone.
On discovering the abuse, the boys' mothers expressed their "sorrow" at finding out the man they regarded as a "kind and generous foreigner" had taken advantage of their children.
In mitigation, Brian Kennedy warned because of his age, Frost could be facing a "de facto" whole life sentence.
Judge Mark Lucraft QC will sentence Frost at the Old Bailey from 2pm.
:: The NCA and NSPCC have set up a helpline for other victims to come forward. The number is 0800 328 0904.