A child rapist, whose crimes were described as among the sickest a judge had seen, has been granted a reduction in his sentence.

Christopher Banham, who photographed and bragged about the abuse to other paedophiles, was jailed for 21 years in January and told he must serve at least three quarters of his sentence behind bars.

But the 36-year-old, formerly of Chesterton Close, Ipswich, could now be released by the end of the decade following a successful appeal on Tuesday.

Banham previously pleaded guilty to three counts of raping a child, four of sexually assaulting a child, and one count of taking and distributing indecent photographs of a child.

His crimes were uncovered after the National Crime Agency made an urgent referral to Suffolk police about the activity of a mobile messenger app user sharing details and images of abuse in a chat group last September.

Sentencing him at Ipswich Crown Court, Judge Emma Peters said Banham's offending was "some of the most repulsive" she had seen.

He was told to serve 14 years of his 21-year term behind bars before being considered for release – with an extended licence period of two years.

On Tuesday, the Court of Appeal cut Banham's sentence to 18-and-a-half-years, with an extended licence period of one year.

Andrew Thompson, representing Banham, made the appeal on two grounds: that the sentencing judge granted only a 30% reduction despite acknowledging that guilty pleas entered at the earliest opportunity earned credit of a full third, and secondly, that closer regard should have been paid to the principle of totality by imposing a sentence which reflected overall criminality while remaining proportionate.

Mr Thompson said it was difficult to see where the judge had made allowances for totality in imposing consecutive terms of 10 and 11 years on two of the three rape counts.

Mrs Justice Lambert said the court did not intend to minimise the serious nature of the offending, but was satisfied that the sentence had been "manifestly excessive".

The court also corrected an error regarding the length of time Banham must serve before being eligible for release. He will now be eligible for release at the halfway point – but only upon referral to the Parole Board by the Secretary of State.

Requirements to sign the sex offenders' register and be the subject of sexual harm prevention order for life remain unchanged.