The Court of Final Appeal, ruling 4-1 on Monday morning, holds that it is “contrary to principle to focus merely on biological features fixed at the time of birth and regarded as immutable”.

The court also noted that in present-day multicultural Hong Kong, the nature of marriage as a social institution had undergone far-reaching changes. It further noted that the importance of procreation as an essential constituent “has much diminished”.

The judgment states that “whether a consensus regarding a transsexual’s right to marry exists among the people of Hong Kong is not a relevant consideration”, because reliance on the absence of a majority consensus as a reason for rejecting a minority’s claim is “inimical in principle to fundamental rights”.

W's solicitor, Michael Vidler, quoted her as saying the decision "is a victory for all women in Hong Kong".

"I may have born a man but after transgender surgery at a government hospital more than five years ago, I've lived my life as a woman and been treated as a woman in all respects except as regards my right to marry.

"This decision rights that wrong, and I'm very happy the Court of [Final] Appeal now recognises my desire to marry my boyfriend one day, and that desire is no different to that of any other woman who seeks the same here in Hong Kong."

Vidler himself called the judgment a "landmark decision".

The top court ruled that the statutory criteria adopted in the Matrimonial Causes Ordinance and the Marriage Ordinance are unconstitutional "since they impair the very essence of the right to marry".

"Viewing the realities of W's position, by denying a post-operative transsexual woman like her the right to marry a man, the statutory provisions in question deny her the right to marry at all. They are therefore unconstitutional," the judgment says.

"We think it would be quite wrong to exclude such a transsexual person from the right to marry in her acquired gender by characterising her as a 'pseudo-type of woman'," said the majority judgment co-written by Chief Justice Geoffrey Ma Tao-li and Permanent Judge Robert Ribeiro.

But the court proposed to suspend carrying out the orders for 12 months because whether new legislation should be enacted is "entirely" a matter for the legislature to decide, it said. W herself, though, will be entitled to the court's decision at the end of the 12-month period whether the new legislation is in place.

If the government fails to amend the Marriage Ordinance according to the judges' order, then that part of the Marriage Ordinance that relates to the case will be considered unconstitutional, Vidler said.

Dissenting judge, Permanent Judge Patrick Chan Siu-Oi said recognising transsexual marriage is "a radical change of the traditional concept of marriage", adding that there is no evidence whether social attitudes in Hong Kong have changed to the extent of abandoning or fundamentally altering the traditional concept of marriage.

He said the change should be made only after public consultation.

On Monday afternoon, W said during a telephone interview arranged by her lawyer: “I am very happy. Finally I can marry my beloved boyfriend in Hong Kong.”

She added that she would now start arranging their wedding.

The Equal Opportunities Commission (EOC) on Monday afternoon also welcomed the top court’s decision and urged the government to amend the Marriage Ordinance accordingly.

"We believe transgender individuals should have the same right as others to live a life of dignity and respect, with full access to participation in every aspect of life," the commission said. "This includes the right to marry the person they love."

"The EOC calls on the government to concretely and promptly take action to address the legal amendment recommended by the Court of Final Appeal,” it said.

Transsexual activist Mimi Wong shares her story in "My struggles as a transsexual in Hong Kong". Video by Hedy Bok