A request by a group of children to a kindly playground supervisor, in Birmingham, to get their ball back began a legal battle which has cost the public purse thousands of pounds in a still mounting legal bill.

The dispute arose after pupils at Alston Primary School asked obliging staff member Mitchell Rogers to retrieve their ball. Legal minds are now tackling the unprecedented legal question whether retrieving soccer balls was part of Mr Roger's job.

The ball had been kicked over a fence and down some basement steps to the school's basement boiler room, which was out of bounds, during the 15-minute morning break. Mr Rogers, of Upton Road, Stechford, was ready to carry out the act of kindness. He used a key to unlock the padlock on a gate at the top of the steps and started down the steps during the playtime on February 14 2003.

But Mr Rogers, described as an assistant learning mentor at the school, slipped and went down the steps on his knees, ending up at the bottom with grazed shins and his head and back hurting

Mr Rogers claimed compensation against his employers, local education authority Birmingham City Council, saying he had had to take a substantial amount of time off work since the fall. The city council said he was only eligible for an injury allowance under the relevant local government regulations if his injury had occurred while he was carrying out work appropriate to his employment.

Council officials turned down his application in March 2003, saying that retrieving footballs from the boiler room area was not his function, and, what was more, he had not been authorised to unlock the padlock at the top of the steps.

In his quest for the ball, he had also wrongly left some 80 children in the playground unsupervised, which was the work he was meant to be doing, said the council. But Mr Rogers took his case to the Office of the Deputy Prime Minister, John Prescott, which polices the local government regulations, and scored an important victory.

The Whitehall referees took the view that retrieving footballs was something he could be required to do as part of his work as playground supervisor, entitling him to his injury allowance.

Unhappy with the result, the city council took the case to the High Court and today levelled the legal score at 1-1 when a judge ruled that Mr Prescott's office had reached a flawed decision and must reconsider.

Mr Justice Henriques, sitting in London, said the case had to be looked at again because a number of questions remained unanswered which were central to the question whether Mr Rogers could be said to be carrying out his work when he went to retrieve the ball. The case now goes back to Mr Prescott's office, which was also ordered to pay the council's legal costs.