LONDON — Demonstrators protesting China's human rights record came close to snuffing out the Olympic torch's flame Sunday during a chaotic relay.

The biggest protests since last month's torch-lighting in Greece tarnished China's hope for a harmonious prelude to a Summer Games celebrating its rise as a global power. Instead, the flame's 85,000-mile journey has become a stage for activists decrying China's recent crackdown on Tibetans and support for Sudan despite civilian deaths in Darfur.

The torch made it unscathed to the O2 Arena in Greenwich after more than seven fraught hours that belied the London event's theme: "Journey of Harmony."

"There was definitely a bit of an edge," British tennis player Tim Henman, one of the torchbearers, told The Associated Press.

Demonstrators attempted to board the bus trailing the torch shortly after British five-time gold medal rower Steve Redgrave started the relay at Wembley Stadium.

Less than an hour later, a protester slipped through a tight police cordon and gripped the torch before he was thrown to the ground and arrested.

"Before I knew what was happening this guy had lurched toward me and was grabbing the torch out of my hand, and I was determinedly clinging on," former children's television host Konnie Huq told British Broadcasting Corp. television.

"I do feel for the cause," she said. "I think that China have got a despicable human rights record."

Another demonstrator tried to snuff the flame with a spray of white powder from a fire extinguisher, police said. Still others threw themselves in the torch's path. They were tackled or dragged off by police. Authorities said 37 people were arrested.

London's Metropolitan police said some 2,000 officers, on foot, motorcycles, bikes, and on horseback tried to keep the procession under control.

One group of Tibetan protesters was corralled in metal barricades across from Bloomsbury Square.

"It feels like we are restrained like a sheep in a barn," said Passang Dolne, 27, a Tibetan national who works as a nurse in London. "It really hurts."

Chinese nationals about 100 yards away were allowed to move freely as they waved Chinese flags distributed by the Chinese Embassy and the Bank of China.

"We don't like the Tibet people who use this time against the Chinese. It's not a proper venue," said Ting Yan, 27.

The demonstration swelled near where Chinese Ambassador Fu Ying was expected to carry the torch. Frantic organizers shuffled the order of participants, and Fu unexpectedly appeared in the heart of Chinatown, jogging unhindered with the torch before handing it to the next runner.