A convicted paedophile has admitted 21 further offences of sexually abusing young boys while overseas.
Christopher Behn, 68, from Colchester, is already serving a nine-year prison term for abusing 11 children in Myanmar in 2016.
The new charges related to the abuse of boys, aged six to 11, in Vietnam.
Behn, who police described as a "committed and prolific transnational child sex offender", is due to be sentenced next month.
The retired engineer appeared in Chelmsford Crown Court by video link from HMP Albany on the Isle of Wight.
Investigators from the National Crime Agency (NCA), Europol and Dutch authorities identified Behn as a member of a Europe-wide network who travelled together to abuse children across the globe.
He was arrested at Gatwick Airport in February 2020, after investigators identified him as appearing in images with another member of the network – a Dutch national who was convicted in the Netherlands.
Behn was detained by officers before he could board a flight to Vietnam.
Photographs taken by Behn, showing him abusing children, were recovered from encrypted electronic devices.
His travel history showed he had visited Vietnam 18 times since 2006, along with trips to Thailand, Philippines, Laos, Cambodia, India, and Myanmar, the NCA said.
He and the Dutch national had also written diaries that described in graphic detail the abuse committed by the pair on many of these trips.
Image source, National Crime AgencyImage caption, Christopher Behn and his network "conspired together via encrypted chats in the hope of hiding their horrific offending", the NCA said
In June this year, Behn was further charged with 23 counts of sexually assaulting a child and causing a child to engage in sexual activity between 2008 and 2018.
He denied two of the charges, but will not face trial on those counts.
Phil Eccles, NCA operations manager, said Behn was "a committed and prolific transnational child sex offender, who dedicated years of his life to this criminal network".
"Behn and his like-minded friends conducted their offending in remote parts of the world and conspired together via encrypted chats in the hope of hiding their horrific offending from law enforcement," he said.
The agency said it had identified a further five men based in the UK believed to have links to the network and investigations were ongoing in a number of countries across Europe.
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