Married in all but the legal sense

When Alexander Cannell married his partner Ian Burford on Wednesday, it marked more than just their 38 years together.

Love, not marriage
The register is open to same-sex and heterosexual couples, one of who must be a London resident

They were the first gay couple in the UK to receive the blessing of the state. After a civic ceremony, they signed the London Partnership Register.

Linda Wilkinson and Carol Budd, who have been together for 16 years, also registered.

Although the register won't give the relationships the same legal status as a marriage, campaigners hope that this is a first step down that road.

Equal rights issue

As well as being seen as a public declaration of love, it is hoped that the register will provide additional evidence in any dispute or civil action over tenancy, pension or immigration rights.

Dutch activist Henk Krol, editor of Gay Krant magazine, first started to campaign for same-sex marriages 16 years ago.

One of the big problems he faced was convincing gay people that they should want to get married.

"Many felt it was old-fashioned. Then six years ago, we started a similar institution to what you now have in London," Mr Krol says.

"That started the whole discussion and people in parliament started to realise that to treat gay people equally, then you have to give them equal rights."

As of last April, the Netherlands became the first in the world to allow same-sex marriages.

'Just a lodger'

In the UK, even same-sex couples who have been together for years are not recognised as official partners in the eyes of the law.

If, for instance, says Mark Watson of news website gay.com, one partner falls seriously ill, his or her live-in lover has no more legal rights than a lodger.

"If you break down a marriage ceremony, there are two elements to it.

"There's the ceremonial stage - the public affirmation of your love, which same-sex couples have been doing for years - and the signing of the legal contract which entitles you to share certain rights and responsibilities."

Timely move

Granting same-sex unions official recognition is a timely move, Mr Watson says.

A number of organisations have been looking at granting gay couples the same pension rights and staff discounts they give married employees.

Paperwork for the children's tax credit, which replaces the married couples allowance, will require applicants to refer to their to spouses as "partners", not husbands and wives.

And a number of test cases to get recognition of same-sex relationships are planned under the Human Rights Act.

Ron Strank, 68, and Roger Fisher, 66 - former nurses planning a test case for equal pensions rights - plan to register their relationship.

"Not that it's going to carry any legal clout - but if sufficient people register, then it might have moral force when the legislation changes in the fullness of time," Mr Strank told BBC News Online.

"We hope that civil registration benefits not just gay people, but straight people in relationships outside marriage."