A married man sexually assaulted children as young as four after promising them sweets and chocolate if they took off their clothes, a court has heard.
Martyn Littell, 40, allegedly lured five boys aged between four and ten into his West Croydon flat in October 2012.
He is accused of "grooming" them after befriending them playing football over the previous fortnight.
He is charged with two counts of child abduction, two counts of sexual assault, one charge of engaging in sexual activity with an eight-year-old boy, nine counts of making indecent videos of children, and possessing indecent images of children.
Prosecutor Gareth Munday told Croydon Crown Court one of the boys, aged six at the time, claims Liddell offered him sweets if he undressed.
The boy allegedly refused but saw his friends putting their clothes on in Liddell's bedroom.
Two other boys, then aged eight and nine, allege Liddell touched them inappropriately in an underground car park.
The eight-year-old also claims Littell performed a sex act on him the next day, later admitting to his mother what happened after she saw them emerging from behind a fence.
Littell, who denies all the charges, claims he saw the boy touching himself and that it led to a conversation about sex.
He told the court: "I did observe him with his hand down his pants and he was obviously playing with his penis.
"I said 'What are you doing?' and he said it felt nice. I said, 'Yes, I'm sure you will enjoy it quite a lot when you get older."
Littell claims the boys then "pestered" him to tell them "the secret" and that he eventually relented and told them "that you use your willy to make babies", as well as explaining foreplay and oral sex.
He said: "I regret ever having a conversation like that with children and realise it was wrong."
Littell suggested the boys could have made up the allegations out of spite because he shouted at them for breaking a jar while in his flat, where he said they were waiting for him to play football while his wife was out.
The trial continues.