A former primary school teacher and youth worker has been jailed today after committing 21 child sexual offences spanning an entire decade.

Paul Cannon, 40, was found guilty of historical sexual abuse against 20 young victims in places including Sutton, Merton and Carshalton from 1999 to 2009, often near the River Wandle.

Cannon, of Coulsdon Road, Coulsdon, was jailed for four years for 21 offences, with a further 20 offences taken into consideration against an additional 19 victims.

These related to 10 offences, mainly of indecent exposure, which took place between 2002 and 2008, Croydon Crown Court heard.

Police have praised a 24-year-old woman who sparked the investigation when she came forward in 2012 having seen the publicity surrounding sexual abuse at the hands of Jimmy Savile.

Victims reported Cannon often wore sunglasses, regardless of the weather, and rode a mountain bike.

In a number of instances Cannon approached the victims - who were mainly female, and aged between six and 13 years-old, engaged them in conversation by asking them for directions to a specific location, and asked them in particular whether they knew if there were any toilets nearby.

On a number of occasions he then asked them if he could take inappropriate pictures of them in exchange for money.

In some cases he then proceeded to sexually assault the victims.

Police said searches at Cannon’s home address unearthed more than 4,000 indecent images and movies of children.

Further images were also found of park areas and swimming pool changing rooms which reinforced suspicions Cannon was and is a serial and prolific offender, a police spokesman said.

Cannon worked at various schools within Surrey and West Sussex.

There are no reports at this time of any offences committed in his capacity as a teacher.

Cannon was found guilty of two counts of indecency towards a child, four counts of indecent assault on a female under 14 years, one of exposure, one count of indecent exposure, five counts of outraging public decency and one of engaging in sexual activity with a child.

Additionally he was found guilty of sexual assault on a child under 13 years-old, sexual assault and five counts of taking indecent images of a child.

Cannon was also sentenced to two months in prison in relation to 12 counts of making indecent images or movies of a child.

He was found not guilty of one count of indecent exposure.

DS Nick Troon, from the Sexual Offences, Exploitation and Child Abuse Command said: "I would like to thank all of the victims in this case and commend them for their bravery in assisting us in bringing Cannon to justice for his crimes.

"A prolific offender, he no doubt thought that given the passage of time he was unlikely to ever be held accountable for his actions.

"I hope today's result will encourage other victims to come forward and report allegations, regardless of the passage of time and nature of the offence.

"I believe there may well be further victims of Cannon out there and would encourage anyone who recognises him in connection with offences to report the matter to police."

Anyone with information is asked to call DS Nick Troon or DC Becky Collins on 020 8217 6431 or 020 8217 6430.