Andrew Faulds, 40, of Greenford, was caught after making a video of the rape that then led to his arrest.
He had previously pleaded guilty at Harrow Crown Court on Monday, 24 March to two counts of oral rape.
On Wednesday, 24, September, he was charged with further offences of possessing and distributing indecent images and sexual activity in the presence of a child under 13.
He pleaded guilty to these offences during the hearing today and was sentenced on all counts to a total of 15 years.
Detectives believe he may have committed yet more offences and are appealing for anyone with information to come forward.
A police investigation was launched after an arrest in Canada resulted in an indecent video being seized.
Enquiries established that the video had been recorded on Saturday, 26 March 2011 on a mobile phone on an estate in Southall.
The information was then sent to the Met Police by the Child Exploitation and Online Protection Centre.
Enquiries identified the victim in the video as a girl with severe learning difficulties and further work then led to the identification of Faulds.
On Friday, 7 March 2014 police attended Faulds' address and arrested him on suspicion of rape.
Seen on the video was a living room that matched the one at an address where Faulds had previously lived.
He was subsequently charged.
Following his initial guilty plea further information came to light that Faulds owned hundreds of indecent images of children, including one that showed him masturbating in the same room as a young girl, on his laptop and mobile phone.
The matters were investigated and Faulds charged with more offences.
Faulds had previously worked as a learning mentor for the Ealing tuition service based in Southall, as a youth worker at Brentford FC Community Sports Trust and for Ealing council's play service. He frequented the Southall, Hayes and Greenford areas.
Investigating officer Detective Constable Emma Macdonald, of the Met's Sexual Offences, Exploitation and Child Abuse Command, said: "Faulds has proven himself to be a predatory paedophile who took advantage in the most despicable way of a young girl with learning difficulties.
"He has an unnatural interest in children that he fuelled by accessing hundreds of indecent images and interacting with other paedophiles online.
"This case demonstrates the world-wide commitment to tackling child abuse and paedophilia and I am pleased this process has led to Faulds' conviction. He has been sentenced to a substantial jail term, thankfully putting him out of reach of other children.
"We believe these offences were not his first and would appeal for any other victims to approach us in confidence."
Anyone with information is asked to contact 020 8246 1901 or Crimestoppers anonymously on 0800 555 111.