At least 250,000 people joined the huge line to see Queen Elizabeth II's coffin lying in state for four days in Westminster Hall.
The figure was released a day after Britain ended 10 days of national mourning for the late monarch, who died on September 8 in Scotland at age 96 after 70 years on the throne.
On Monday, hundreds of world leaders and dignitaries attended her state funeral at Westminster Abbey, and huge crowds thronged the streets of London and Windsor to bid a final farewell to their Queen before she was laid to rest in Windsor.
Culture Secretary Michelle Donelan said officials were still "crunching the numbers" but estimated that about a quarter of a million people joined the longest queue most have ever seen for a chance to file past the Queen's coffin from September 14 until shortly before her state funeral on Monday.
Many in the queue waited for up to 13 hours, braving the autumnal chill and spending entire nights shuffling for kilometres along the River Thames to pay their respects. The London Ambulance Service said staff and volunteers cared for around 2000 people who lined up, and took 240 in for hospital treatment.
The Queen was interred late Monday alongside her late husband Prince Philip and her parents in Windsor Castle's St George's Chapel, a gothic church steeped in royal history for centuries.
Outside Windsor Castle on Tuesday, cleaners were busy clearing up and international news crews were taking down their equipment a day after thousands packed the streets to view the military procession escorting the Queen's coffin from London to Windsor.
"The nation certainly has come together. As for the crowd yesterday, it was unbelievable, really," said Marion Brettle, 73. "I think the whole nation stopped, and thought, and listened, and watched."
The royal family were observing another week of mourning and aren't expected to carry out official engagements. British media including Sky News reported that King Charles III and his wife Camilla, the Queen Consort, flew to Scotland on Tuesday to grieve privately.
Flags on British government buildings returned to flying at full-staff Tuesday, but those at royal residences will remain at half-staff until after the final day of royal mourning. — AP