Thousands of gay couples will publish their "wedding banns" today as the long-awaited Civil Partnership Act comes into force.
Same-sex couples who register their names with local councils today will be able to marry from 21 December, after an obligatory 15-day "cooling off" period.
The legalisation of gay marriage is expected to generate a multimillion-pound economy in wedding ceremonies, receptions and gifts, with businesses keen to cash in on the market.
With some couples having waited more than 40 years for the right to marry, industry observers say the power of the "pink pound" is likely soar.
The Act gives gay couples the same inheritance, pension, tax and benefit rights as married heterosexuals.
They will also have legal "next of kin" status and, in the event of separation, will have rights over each other's assets and access arrangements to any children from the relationship.
Celebrities such as Elton John and George Michael have said they are planning to marry their respective partners in the next few months.
Lawyers have already scented a lucrative new niche, with many rushing to counsel couples about pre-nuptial agreements and other advice before they tie the knot. But the biggest boom will come from the market in wedding services.
Ben Spence set up his internet company, Pink Products, specifically to cater for the gay marriage business. He said: "The traffic has been simply phenomenal in the last few weeks, with about 3,000 hits a day. You have to remember that these are people with enormous spending power and some have waited decades for a law like this.
"I know people who are planning to spend up to £60,000 on their wedding day because they want it to be special."
Among the most popular items from Pink Products are "his and his" cake figurines (sculpted to look different from each other), personalised chocolate wedding favours and "just married" thongs.
With the "pink pound" estimated to be worth £5bn in Britain, companies such as Hilton Hotels, the Jane Asher cake company and the John Lewis Partnership are already advertising with Mr Spence's company.
The gay wedding market will be worth about £600m a year, according to a study by Out Now Consulting, a marketing firm.
A spokeswoman for John Lewis said: "We have a very established wedding gift list for couples who are getting married and we want to offer the same level of service to same sex couples."
Virgin Holidays is now offering package tours, including a civil partnership ceremony, to Florida and Hawaii. Even the high street chain Superdrug has got in on the act, offering an embroidered "dearest and queerest" towel set, with a proportion of profits going to the Elton John Aids Foundation.
About 22,000 couples are expected to go through the 20-minute civil partnership ceremony in the next five years, according to government predictions.
The gay rights group Stonewall estimates that eventually half of all gay and lesbian couples will marry.
Some religions are getting involved, with the Liberal Judaism sect the first to offer a liturgy for partnership ceremonies, while the Methodist church is currently conducting a review of ways in which it could offer blessing services for same-sex couples.
The Church of England has ruled that clergy should not hold official blessing services for couples, but can pray for them.
Ceremonial hot spots
* BRIGHTON: The council will oversee the first civil partnerships in Britain, as three couples aim to tie the knot at 8am on 21 December, the earliest time possible. More than 400 couples have pre-registered for a ceremony.
* MANCHESTER: Hundreds of couples attended a Gay Wedding Show exhibition last month. The new legislation was welcomed with a party in August, when couples were invited to sign a "pink book" pre-registering their civil partnerships declaration.
* LONDON: Islington, Westminster and Kensington and Chelsea are the boroughs with the most couples booked in for a ceremony. The London Eye is proving a popular venuewith a package that includes a capsule bedecked with flowers.
* SCOTLAND: Edinburgh has about 60 couples booked for a ceremony, while Glasgow has 30 planned within the next month. Gay clubs have rushed to become licensed for civil partnership ceremonies and offer "all-in-one" packages.
Big plans for a very special day: Ciaran Quigley and James Hagger
Ciaran Quigley and James Hagger, both 23, are planning a civil partnership ceremony for February and plan to spend up to £40,000.
"We have gone through a commitment ceremony but as soon as we heard about the new law we said we wanted to do it," Mr Quigley said. " For us, it's about saying we love each other in front of our friends and family, but we also want to have a huge party.
"Heterosexual weddings cost about £20,000, and we thought that anything they can do, we can do better!"
The couple, who work in marketing, have been together for three years and live in Middlesex.
They are planning a country house reception with a sit-down meal for at least 100 people. Entertainment includes a string quartet, followed by a disco and a drag act.
"We are prepared to splash out because it is going to be our special day," said Mr Quigley. We have faced some bigotry in our lives and we have been through some tough times, so this is going to be a really important day for us."Reuse content