Predator Barry Britton, who lived in Westminster, befriended a family until they felt safe leaving him alone with their toddler.
He then abused his position of trust and sexually abused the young boy.
Britton was jailed for life with a minimum term of just five years in 2014.
In 2020 he was further convicted of a catalogue of sexual abuse against two young girls which dated back as far as the 1970s.
Over the course of 30 years he subjected the two girls to a series of sexual attacks.
For these offences he was jailed for a further nine years.
It has now been revealed that the 73-year-old died of lung cancer in August 2021 while a prisoner of HMP Whatton.
He was diagnosed in May 2021 before he died on August 3.
A coroner ruled that he died of natural causes.