Two years on, and it is now mainstream for gay couples to be tying the knot.
By Claire Marshall
About 18,000 civil partnership ceremonies have been held
After 16 years together, Craig Davidson and Steven Butterill have come to Brighton Town Hall for their civil partnership ceremony.
To the strains of It Had to Be You, they walk in to a room filled with their friends and family. They make their formal declarations of love, exchange rings, and sign the register.
The process lasts around 25 minutes, with the registrar finally announcing, "It gives me very great pleasure indeed to say that you are now legal partners for life".
They look delighted.
All the way
I ask why they have chosen to formalise their relationship, and Steven says: "We thought it was important - that with the opportunity there, that committed gay couples should take advantage of it".
Craig adds: "We think that you can either be half-way committed or all-the-way committed - this was our opportunity to say we are all-the-way committed".
Many other people in a gay relationship are taking the same step.
On Saturday, Brighton Town Hall will see the 1000th couple go through a civil partnership ceremony.
Across the UK, more than 18,000 ceremonies have been performed since 2005.
Debra Reynolds, the civil partnership registrar in Brighton, told the BBC: "It's gone brilliantly. Sometimes during the summer months on a Saturday, three-quarters of the registrations are civil partnerships as opposed to marriages".
Perhaps predictably, though, the negative side is starting to emerge. Lawyers across the country are reporting a steady trickle of applications to dissolve their partnerships.
Kahn Priestly, a family lawyer with Healy's in Brighton, believes that this will start becoming a big part of her job.
She said: "It's inevitable there are going to be more dissolutions. We are just entering the territory where people can agree to dissolve their partnership after a period of separation.
"Lots of people have gone into them without actually realising they had any kind of legal significance, and that when they want to separate they have to go through a legal process to do it.".
But the first couple in England to have a civil partnership are still very positive about it.
Debbie and Elaine Gaston also tied the knot in Brighton. Debbie said: "I don't think it changed our relationship, but it deepened it."
Elaine adds: "Yes, it did - it made it stronger and it strengthened it. I'm not so scared about checking in to hotels as a couple any more."