A controversial decision by Northern Ireland Health Minister Ms Bairbre de Brun to centralise maternity services for Belfast at the Royal group of hospitals site was quashed in the High Court yesterday.
Mr Justice Coghlin, in a judicial review, overturned Ms de Brun's decision to opt for the Royal instead of Belfast City Hospital (BCH).
The judge said the Minister required urgent advice and seemed to have taken her decision within two days of receiving briefing papers.
"She did not properly appreciate the nature of her discretion in relation to the linkage between gynaecology and maternity services," he said.
"She expressed the choice of sites to be `close' and `in the final analysis' one of the two factors which persuaded her of the clinical argument in favour of the Royal site was its proximity to the accident and emergency department."
Mr Justice Coghlin said this linkage had not previously featured during the long history of the decision-making process and those seeking to argue in favour of the BCH site were given no opportunity to make representations on this issue.
The ruling was the latest in five years of wrangling over the controversial issue. Last January Ms de Brun announced the decision to site maternity services in a new hospital at the Royal. In May the Jubilee Maternity Hospital closed and services were transferred to the existing maternity facility at the Royal.
The judicial review was brought by Mrs Kathy Hindes, whose first four children were born in the Jubilee.
Ms Pat Duke of the Jubilee Action Group said: "We are absolutely delighted and just feel that justice has been done at last.
"Of course it is tinged with sadness as the Jubilee has gone but we are pleased that the whole matter will now have to be looked at again."
Mr Pat Haines, director of planning at BCH, said: "The site originally proposed for a combined maternity unit alongside the [BCH] Tower remains available."
The Department of Health said in a statement: "We will have to look carefully at this judgment before making further comment."
Sinn Fein's spokesman on health, Mr John Kelly, said the Royal was still the best site for new maternity services and that the judgement referred only to how Ms de Brun's decision had been made and did not mean it was wrong.