Susan Edwards, one of only 21 female London Underground drivers out of a workforce of more than 2,000, complained that she was forced to take voluntary severance pay because a new rostering system meant she would have to work early and late shifts.
Three appeal judges ruled that the imposition of the new shift system in 1992 amounted to discrimination because it had a far greater impact on women drivers than it did on male colleagues.
This was because it was difficult for people with responsibility for children to work the new shifts - and many more women than men had responsibility for children.
The judges unanimously dismissed a London Underground appeal against rulings in Ms Edwards' favour by an industrial tribunal in 1995 and the Employment Appeals Tribunal in January 1997.
After yesterday's ruling, Miss Edwards, 39, said: "I am delighted that after all these years the court has upheld my claim that I was unlawfully discriminated against."
Now studying social sciences with the Open University, she added: "It simply was not possible to bring up my son Charlie [now 11] and work the new rosters. I had worked for London Underground for nine years and looked after my son and it was only the new rosters which stopped me from carrying on."
The Equal Opportunities Commission, which had backed Miss Edwards' case, said the judgment "means employers must consider the needs of their employees before changing the way they work".
The Maternity Alliance said Miss Edwards' victory was wonderful news for the thousands of new mothers who wanted to return to work after maternity leave on hours that fit in with childcare.
Legal officer Joanna Wade said: "This is a significant step towards a legal right to baby-friendly workplaces. At present, many women give up their jobs rather than struggle through the minefield of incorrect sex discrimination legislation."
London Transport said in a statement: "London Transport is a committed equal opportunities employer and in the light of today's judgment we will be more determined than ever to demonstrate this fact.
"Train operators have always been able to exchange shifts with other operators and that remains the case today."
Asking for leave to appeal to the House of Lords, Ingrid Simler, for the company, told the court: "This appeal has raised matters of some importance in relations to sex discrimination claims."
Lord Justice Simon Brown acknowledged that it was an important case but said the Law Lords themselves should be left to decide whether they wanted to intervene.
Lawyers for Miss Edwards said a fresh tribunal hearing would have to take place to assess how much compensation she should receive. But it is unlikely to be held until a decision is made on whether the case will go to the Lords.
An employment law expert said the decision was good news for women and should make it easier to prove that a change in shift patterns was discriminatory.
Mary Stacey, head of equality at Thompsons solicitors, said the ruling showed that a smaller proportion of women than men can cope with changes to shift patterns. "Shift working is on the increase in many sectors, including retailing and banking, and this decision should give encouragement to women who are having difficulties juggling shift patterns with family responsibilities."Reuse content