The National Crime Agency arrested Huckle at Gatwick airport, where they found a camera, phone and computer with 20,000 images of child abuse in his luggage.
NCA head of operations Tony Cook described Huckle as a “lone offender” who had used a pseudonym and stated he was living in India in order to cover his tracks.
Mr Cook said Huckle used an electronic ledger to give himself a points score for his level of abuse per victim.
Mr Cook said: “This goes to show the scale of depravity. There is no doubt the quantity this offending would have increased had he not been arrested.
“He is only 30 years of age so we can only imagine what sort of offending he had in front of him.”