A child rapist whose crimes were described as among the sickest a judge had ever seen has been jailed for 21 years.

Christopher Banham, who documented the abuse and bragged about it to other paedophiles, will have to serve at least three quarters behind bars before being considered for release.

The 35-year-old's offending was labelled "repulsive" by sentencing judge Emma Peters at Ipswich Crown Court on Monday.

Banham, of Chesterton Close, Ipswich, had already admitted three counts of raping a child under 13, four of sexually assaulting a child by penetration, and taking and distributing indecent photographs of a child.

The court heard how Banham's crimes were uncovered after the National Crime Agency made an urgent referral to Suffolk Constabulary, alerting the force to the activity of a mobile messenger app user – identified as Banham via his IP address – sharing details and images of the abuse in a chat group.

Prosecutor Joanne Eley said indecent images were found on Banham's phone following his almost immediate arrest in September last year.

Andrew Thompson, mitigating, said Banham had expressed shame and disgust for his crimes, which he admitted at the earliest opportunity by indicating his guilt before magistrates.

Judge Peters said Banham's online messages made for sickening reading, adding: "It's hard to conceive of a more compelling case of guilt.

"It's clear this is some of the most repulsive offending I have seen as a judge."

Banham will have to serve 14 years in jail before being considered for release. Any period served on licence will be extended by two years.

He will also have to sign the sex offenders' register and be the subject of sexual harm prevention order for life.

Following the hearing, Pc Chloe Bilner, of Suffolk Constabulary's south safeguarding investigations unit, said the sentence reflected the severity of Banham's "truly shocking and despicable crimes", adding: "The impact of offences such as these on the victims is immeasurable and cause untold trauma and suffering.

"We are continually grateful for the bravery shown by survivors of sexual abuse in speaking to us and helping us to ensure justice is done.

"I hope the outcome of this case reassures members of the public that we take these allegations extremely seriously and work to safeguard victims as quickly as possible.”