A huge party for Londoners is promised Saturday as more than a million people are expected at the city's annual Gay Pride parade and festival.

But the idea of an extravagant party for gay men and lesbians seems to have caused controversy in the British capital.

Pride London's theme is “Come out and play” as the rest of the world celebrates the 40th anniversary of the birth of the modern gay rights movement, the Stonewall Inn uprising.

In 1969, the patrons of the Stonewall Inn, a popular joint for drag queens and transvestites, fought back against the New York City police, who often harassed patrons at gay-friendly bars. For days, thousands joined in demonstrating against the police.

“I'm shocked that Pride London has hardly mentioned the 40th anniversary of the Stonewall riots on its website or in its magazine,” gay rights advocate Peter Tatchell told the Guardian. “Most of the content is about entertainment and partying. To ignore and downplay this important anniversary is an insult to the veterans who began our momentous fight for freedom.”

Anisas de Jong, director of the UK Lesbian and Gay Immigration Group, agreed: “Gay Pride should be providing more of a political space in line with its history which is about visibility being a political statement in itself. The whole Pride issue is not just about celebrating our identity but about making a political statement about our identity and addressing injustices.”

Pride London organizers, however, defended their decision not to focus on the anniversary, saying it would be preaching to the choir and that the Stonewall anniversary would “get a lot of mainstream press interest” anyway.

The carnival stepped off at 1PM Saturday as go-go boys atop rainbow waving floats wound through crowded London streets from Baker Street to Trafalgar Square, where a full day of entertainment awaits revelers.

Tatchell brought his own political statement. Standing along the route, he was photographed holding a sign that read “Gordon & Sarah can marry, gays can't. End the ban on gay marriage,” a reference to Prime Minister Gordon Brown and his wife, Sarah. Sarah Brown was among the many celebrities marching in the parade.

The UK recognizes gay and lesbian unions with civil partnerships, not marriage. Tatchell, one of Britain's best known gay activists, has called the legal divide “a form of sexual apartheid.”

London will be the site of an even larger gay party when it hosts WorldPride in 2012.