The torch - carried by athletes, charity workers and celebrities - thrilled thousands of Londoners as it swept across Regent's Canal in Camden, through the city's newly renovated neo-gothic train station at St. Pancras and down the winding streets of the ancient City of London.
For many Londoners, it was their first glimpse of a golden beacon that has spent the past 68 days traveling up and down the country, from Loch Ness to Land's End, as well as going across the water to Ireland and Northern Ireland.
In the north London neighborhood of Camden, many families with young children got up early to cheer as the torch kicked off its relay at the Victorian-era Roundhouse music hall around 6:50 a.m. Others simply hadn't been to bed.
"It was pretty cool to see it actually," said 19-year-old Anastasia Gribaldi, a Goth who had been out all night clubbing. "It was like: 'Wow, it's the torch!' We weren't expecting it."
The torch completes its 70-day, 8,000-mile (12,900-kilometer) journey on Friday, lighting the Olympic Stadium's cauldron in a ceremony marking the official start of the 2012 London Games. The identity of the final torchbearer is still a closely guarded secret.
On Thursday, the torch was carried past some of the city's most impressive landmarks, including the Houses of Parliament, 10 Downing St. and Buckingham Palace, where it was greeted by Prince William and his wife Kate, the Duchess of Cambridge.
Earlier in the day it sped across London's River Thames along with Paralympic champion Ade Adipitan, whose dreadlocks flapped in the wind as he propelled his wheelchair across the slender Millennium Bridge.
Londoners who have spent much of the past few weeks worrying about rain, Olympic security, and strikes appeared to lighten up.
In the south London borough of Lambeth, flag-waving crowds chanted "We want the torch!" In nearby Wandsworth, 24-year-old John Lake - a cancer survivor who has raised thousands for the Brain Research Trust - pumped his fist and waved the torch back and forth as he ran down the road with a mile-wide grin.
"Make some noise!" someone shouted as the crowd erupted into cheers.
The crowds thickened further as the torch made its way back across the Thames, with Joanna Lumley and Jennifer Saunders - who played Patsy and Edina in the British comedy "Absolutely Fabulous" - taking the flame for a jaunty walk in London's wealthy Chelsea neighborhood.
On Oxford Street, London's famous shopping thoroughfare, the torch rode on an open-topped, double-decker bus.
Still, not everyone was caught up in the Olympic excitement.
"It was pretty convenient that it came through as I was getting my morning coffee," said Jack Tate, a 28-year-old retail worker in Camden. "Now I can say I've seen it. There's no need to watch any more of this Olympics rubbish for the next few weeks."
Paisley Dodds and Sheila Norman-Culp contributed to this report.