A retired teacher who abused children for decades both in the UK and abroad has admitted 45 sex offences in one of the worst cases to come to court.
Mark Frost, known as Andrew Tracey, pleaded guilty at the Old Bailey to a catalogue of abuse against nine children in Thailand between 2009 and 2012.
After the allegations emerged in Asia, two former pupils of a school in Worcestershire came forward claiming they too were sexually assaulted by the English teacher in the 1990s.
Frost, now 70, had sex with one of the boys in a school store room, at his home where he lived with his adopted son, and in a car park in Woking.
He admitted charges relating to the historical abuse, although one of the victims died before he was brought to account.
His crimes included multiple rapes, indecent assault, inciting children to engage in sexual activity and making indecent images.
Prosecutor Ruona Iguyovwe said: Sentence is obviously a matter for the courts but we would rank it as one of the most serious ones we have come across.
Frost was at the centre of a complex international investigation involving the National Crime Agency and authorities in Canada, 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 sexual predator tried to adopt a son through the Catholic Church and was turned down – but eventually succeeded through a local authority.
He reached a senior position in the Scouts after joining in 1967 but resigned in 1991 before his first conviction.
By 1992, he admitted possessing indecent photographs of a child and was fined £200 by Evesham magistrates.
In 1993 he was jailed for a year at Worcester Crown Court for allowing his premises to be used for drugs and sex with an under-age girl.
But it was not until three years later that Frost was banned from teaching.
He was jailed in 1998 for a year at Luton Crown Court for indecent assault on a male under 16 and put on the sex offenders’ register for 10 years.
An 11-year gap in known offending followed as Frost moved from place to place.
Police in Guernsey investigated Frost in the early 2000s in connection with indecent images of children on the internet.
After he came off the sex offenders’ register, he moved to Thailand and abused boys there but skipped bail and returned to Britain.
Frost then fled to Spain and was finally extradited from Alicante back to the UK last year after Dutch police uncovered incriminating web chats on a computer in the Netherlands.
He is expected to be sentenced later today.
:: The NCA fears many more youngsters may have fallen victim to Frost. The hotline for those who may have been affected is 0800 3280904.