John Roberts, 63, who was on the run from prison when he was taken on by a London council, was told by Judge Alan Hitching that he was facing a life term.
An Old Bailey jury convicted him of sexually abusing two boys aged seven and 13. Both have been left traumatised by their ordeal, it was revealed.
Roberts went on the run from jail while on home leave from an eight-year sentence and took an assumed name of William Lane.
He went to an employment agency and applied for the job of groundsman for Kennington Astroturf football pitch in south London. Lambeth council gave him the job at the pitch, which is used by hundreds of youngsters in the borough.
The court was not told whether the council had made any police checks.
Police revealed afterwards that he was in the process of starting up several boys' football teams when he was arrested.
Roberts, of Peckham, south London, was found guilty of buggering and indecent assault on the seven-year-old and indecency with the 13-year- old. He was cleared of one charge of indecency with the younger boy. The offences occurred in October last year.
Roberts cursed the jury and continually interrupted the proceedings after the guilty verdicts. He was ordered to sit down and keep quiet or face being taken to the cells.
The judge told him: "This is the ninth offence of this nature and his passion in this direction is showing no signs of abating. I have to consider a very long jail term or a life sentence for the protection of the public and young children."
He adjourned the case for pre-sentence and probation reports to be prepared. The judge also extended legal aid to Roberts' defence team so a top QC could be employed to argue his case as he is facing such a long penalty.
Roberts worked for Lambeth for four months using his position of trust as a means of getting close to children, the court heard.
Edmond Brown, prosecuting, said: "He used his influence and his age to take advantage of two boys and invite them into his house."
The court heard that he enticed the boys with money and by taking them to hamburger restaurants. The boys, who were not allowed to have any counselling until after the trial, gave their evidence via a video link.
A father of one of the boys saw Roberts follow his son into bushes at the ground and later warned him off.
But Roberts continued his activities. He gave the 13-year-old boy pounds 15 and showed him and his seven-year-old friend pornographic pictures of children.
He carried out the attacks at his flat and when police raided it they found a Polaroid camera, gay magazines and condoms. He was caught after one of the boys told his father.Reuse content