The decision by the British parliament to allow same-sex marriage was a momentous one.
Equally dramatic has been the transformation in the rights of same-sex couples in the dozen years since the Netherlands became the world's first country to allow gay marriage.
However, by the time the first gay weddings are held in England and Wales next year, there will be only 17 countries across the world which permit marriages between individuals of the same gender.
In addition to disparities in how gay couples are legally recognised around the world, there are variations within certain countries in how such relationships are regarded. The same patchwork nature also applies to the status afforded to civil partnerships.
This can lead to considerable complications for those involved, especially for the growing number of individals whose domestic and professional lives take them away from those territories in which their marriages or civil relationships have been formalised.
It is perhaps surprising to consider how many Britons form part of an increasingly international labour market. In the 12 months to September last year, for example, more than one third of a million people emigrated from the UK. Fifty-eight per cent of those went to take up or to find employment.
Those in civil partnerships who join the exodus from Britain will find that the rights to which they are entitled depends greatly on the country to which they move, whether in Europe or further afield.
In the United States, for instance, gay marriage is possible in 13 states. Of the other 37 states in which same-sex marriage is currently not permitted, only six allow civil unions - the equivalent of a UK civil partnership.
This picture is further complicated by a number of US states which deny same-sex couples either form of legal union but are happy to conduct divorce proceedings for those gay couples whose marriages do not last the course.
In Europe, things are equally unclear. Five years before the UK allowed its first civil partnership, France passed a law allowing the creation of something called a Pacte Civil de Solidarite (or PACS, for short).
The UK equivalent of the PACS, the civil partnership, is only available to homosexual couples, while the French document gives both gay and heterosexual couples a measure of legal and taxation protection, including exemption from inheritance or succession tax and the ability to file joint tax returns.
The British Government intended that civil partnerships provide gay couples with similar tax treatment and legal rights to those enjoyed by married couples.
However, when they crossed the Channel, many Britons found that France did not recognise their civil partnerships, meaning that they might not have any special treatment on succession. They were also subject to the full inheritance tax rate of 60 per cent.
The advice which they received from the French authorities was that differences between the two systems meant the best way to proceed would be to dissolve the arrangements taken out in the UK and enter into a PACS.
The frustration for those put in that quandary was magnified by the fact that although a PACS offered fewer beneficial provisions, French citizens separating in the UK would have their PACS treated as a civil partnership by the courts here with the greater degree of security which they offered.
Although civil partnerships were finally recognised under a change in French law in April 2009, the differences in status remain.
European Union officials have taken steps to simplify matters. A regulation called Brussels ii bis came into effect in March 2005, allowing family law matters to be dealt with by one country applying the law of another EU state, if considered appropriate.
Although this can be argued as amounting to progress, it has led to difficulties of its own. Despite greater fluidity in the cross-border job market, there are still few family lawyers to be found across the Continent with the qualifications to practice in more than one state.
Furthermore, given that family law, in particular, is usually designed to be applied according to the circumstances of the individuals involved, there will inevitably be variations in how - for example - an Irish judge interprets British legislation and imposes it on a British couple living in Ireland.
For anyone in a civil partnership, advice from legal practitioners experienced in family law at home and in their country of destination is a must before they leave our shores. Otherwise, they may risk their futures being left open to interpretation.