Tenths of thousands of people are expected to travel to the centre of London to pay their respects to the late Queen Elizabeth II as she lies in state at Westminster Hall.
Transport for London (TfL) said that accommodating the transport needs of all the mourners is the "biggest event and challenge” the organisation has faced in its history.
Only yesterday, TfL figures showed more than 19,000 people started or finished journeys at Hyde Park Corner station, double the total on the same day last week. Across the Tube network as a whole, TfL recorded 2.99 million journeys on Tuesday, up 8 per cent compared with a week earlier.
"The most recent approximation or estimate is that there will be around potentially up to 750,000 people in the queue for lying in state, which is itself a huge number," Byford said. "But then if you take the whole 10-day mourning period and the various events that happen during that - obviously some happened elsewhere...