Cameras flickered as hordes of photographers and fans huddled together in the cobbled streets around Windsor's town hall, the Guildhall, where Prince Charles and Camilla Parker Bowles wed in April. John, 58, and Furnish, 43, walked out smiling, waving and raising their thumbs after the ceremony as an attendant threw rice at the couple.
After the ceremony, John and Furnish celebrated over a quiet lunch with their parents, reports CBS News reporter Larry Miller
Later, in at least three big circus tents on the grounds of their mansion, 700 guests will be drinking pink champagne and partying big time. The reception and lamb dinner is said to be costing $2 million.
The couple are among hundreds of same-sex couples to wed inin England and Wales on Wednesday, the first day that such ceremonies become possible. Ceremonies were held earlier this week in Northern Ireland and Scotland.
Three couples signed their documents moments after the register office opened at 8 a.m. (0800 GMT) in Brighton, the south coast city known as Britain's gay capital.
Suzi Uprichard, 33, of Maidenhead, among the crowd in Windsor, was excited to be at what she described as a historic day for same-sex couples.
"It's a long time coming really," Uprichard said. "Admittedly, it's Elton and David's day, but it's the first day that gay couples can engage in civil ceremonies in ... England. So I think it's something celebrate."
Police erected security barriers outside building but expected no trouble. Relaxed officers, some on horseback, chatted with photographers, who stood four and five deep on the streets outside the Guildhall.
Fans got into the spirit of the event with posters featuring the couple and Queen Elizabeth II, who has a castle in Windsor, a centuries-old seat of British royalty west of London. A nearby shop wished the couple well with handpainted sign saying "go for it."
Gay rights activists see the unions as joyous — and important in advancing efforts to give same-sex couples the same rights as heterosexuals. Peter Tatchell, spokesman for the gay and lesbian human rights group OutRage! said the wedding "would raise the profile of gay love and commitment."
"Their same-sex civil partnership ceremony will be reported all over the world including in countries where news about gay issues is normally never reported," he said. "This will give hope to millions of isolated, vulnerable, lesbian and gay people especially those living in repressive and homophobic countries."
Furnish, a Canadian-born filmmaker, and John have been together for 12 years.
Their reception is expected to be a star-studded extravaganza.
British tabloids claim the giant white tents will be heated adequately to warm the hundreds of guests in skimpy evening gowns.
Guests at the couple's bachelor night on Monday — a prelude to the bigger reception on Wednesday — included heavy metal rocker turned reality TV star Ozzy Osbourne and his wife Sharon, model and actress Liz Hurley and musicians Bryan Adams, Gary Barlow and Kid Rock.
The new law — passed last year despite some opposition from Parliament's unelected House of Lords — allows civil ceremonies that will give same-sex couples the same social security, tax, pension and inheritance rights as married couples.
John and Furnish acknowledged that their ceremony might have broader ramifications.
"As far as I'm concerned I've always considered myself committed to Elton and he's the person that I want to spend the rest of my life with. So in that sense I don't feel like the dynamic of our relationship is going to change," Furnish told Attitude magazine. "But from a social standpoint, I think its hugely significant. It is a major, major change. It is one of the defining issues of our times."