A man who was part of a teenage gang that left another man to die on a riverbank six years ago has been jailed for nine years for the rape and sexual assault of a child under 13.

Anthony Walker, 24, previously of Catton Grove Road, Norwich, was also placed indefinitely on the sex offenders' register.

Norwich Crown Court was told that Walker, who pleaded guilty to rape and sexual assault, had known his victim, who cannot be named for legal reasons.

He was jailed for nine years in total with eight for rape, five years for sexual assault, to run concurrently, and one year for an unrelated matter.

Five years ago, Walker was jailed for three years for being part of a teenage gang that robbed 31-year-old David Lucas, who was left to die on the city's riverbank.

Walker, who had pleaded guilty to robbery, was involved in the attack on Mr Lucas, which took place in the early hours of July 2, 2005. Dean Cullen, then 19 and of Lawson Road, New Catton, was the ringleader of the group and was jailed for life in 2006, and told he must serve a minimum of 20 years after pleading guilty to the murder.

Michael Moss, then 19 and of Spencer Road, Norwich, also pleaded guilty to robbery and was sentenced to three-and-a-half years, and Alan McHugh, then 34 and of Shipfields, Norwich, was jailed for four years after pleading guilty to perverting the course of justice.

The court had been told that Walker, Moss and Cullen had lured Mr Lucas to the riverbank on the pretence of a drugs deal, where Cullen punched him and Walker brought Mr Lucas to the ground.

Moss kicked him as Cullen sat on Mr Lucas's stomach and removed the cash which Mr Lucas had, using a stolen credit card from his pocket.

Walker and Moss then fled while Cullen stamped on Mr Lucas's head at least five times as he lay motionless in a pool of blood, as he feared he would grass on the group.

McHugh, learning of the attack, later returned to the scene and pushed Mr Lucas, who may have still been breathing, into the river.

His body was found floating in the River Wensum, near Whitefriars Bridge, in Norwich.

After their son's attackers were jailed, Isabel and Brian Lucas criticised the sentences handed to Walker and Moss. They said that without the pair's involvement in the assault, Cullen would never have been able to murder their son, and added that all the men, including McHugh, were collectively responsible for his death.