Hillingdon Council has been left with huge legal costs after it dumped a young asylum seeker in Liverpool, claiming he was that city's responsibility.
A council support worker took the boy, known as AK, to Liverpool in May last year and left him in the city's municipal building with a letter explaining why he was there.
The dispute over who is responsible for AK started shortly after he arrived in the UK from Pakistan with a false passport in April last year.
He sought asylum in Liverpool, claiming he was 15 and entitled to all the special help due to a "child in need".
However, when the City Council decided he was actually 18 his case was referred to the Home Office and he was sent to Harmondsworth Detention Centre, in Bath Road, Longford.
He was then escorted back to Liverpool by the council official after his lawyers obtained an independent medical report, supporting his plea that he was aged just 15, which was accepted by an immigration judge.
Last Tuesday, Appeal Court judges decided in favour of Liverpool, saying Hillingdon had failed to give any consideration to the boy's welfare needs, instead taking the "simplistic view" that his wish to live in Liverpool was "determinative of the matter".
Lord Justice Dyson, sitting with Lord Justice Rix and Lord Justice Wilson, ruled the responsibility for caring for the boy lay firmly with Hillingdon. The council will now have to find him accommodation and reach a final assessment of how old he is, as well as having to pay the heavy legal costs.
Julian Wooster, deputy director of children and families at Hillingdon Council, said: "We would strongly refute that Hillingdon has behaved improperly in this case and we are considering whether to appeal against this latest judgement."