The Elizabeth line is to be brought back into service on Sunday for the first time since the Platinum Jubilee weekend to help people to pay their respects to the Queen.
The £20bn line, renamed from Crossrail in honour of the Queen and formally unveiled by the monarch in May in one of her final public engagements, had only been operating six days a week to allow engineering upgrades to take place.
But it was announced on Monday that the line’s central section, between Paddington and Abbey Wood, would be open on Sunday September 18, the day prior to the Queen’s funeral, with 12 trains an hour in each direction.
This will ease the pressure on the London Underground, which last weekend had to implement station closures to cope with the number of people heading to Buckingham Palace to pay their respects.
Crowds are expected to grow further when the Queen’s coffin arrives in London on Wednesday and the laying-in-state opens at Westminster Hall.
The Elizabeth line had been expected to remain closed on Sundays until the next phase of its opening - the linking of its eastern and western branches with the central tunnel section - happens on November 6.
About a million people are thought likely to seek to view the coffin, with Westminster Hall remaining open 24 hours a day until 6.30am next Monday, prior to the coffin being readied for the funeral at Westminster Abbey.
Network Rail said on Monday that crowd levels this week were expected to be “unprecedented”, especially from Wednesday, with the capital “exceptionally busy”.
Advice issued in conjunction with Transport for London and the Rail Delivery Group warned of Tube stations being closed at short notice - and appealed to passengers to avoid Green Park station, the closest Tube to the palace.
Rail passengers were advised to consider walking the final part of their journey rather than boarding a Tube train.
On Sunday afternoon, Victoria line passengers were told that Green Park was shut, with trains not stopping at the station.
Widespread road closures are in place, with the CS3 east-west cycle superhighway route via Green Park and St James’s Park closed.
Tube trains may not stop at all stations and changes to entries and exits may be introduced to create a “one way” system to prevent overcrowding.
Sir Peter Hendy, chairman of Network Rail said: “The transport industry is working hard to help people pay their respects in London and across the United Kingdom. Please make sure you check before you travel as we expect the road and transport networks to be busy.
“For up-to-date travel information please check www.nationalrail.co.uk or your train operator’s website. For London travel information visit www.tfl.gov.uk.”
TfL commissioner Andy Byford said: “At such an important and difficult time for the country, we are doing everything we can to ensure Londoners and visitors can pay their respects to Her Majesty The Queen and welcome His Majesty the King.
“We are working with our partners to keep our city moving smoothly and to ensure that everyone who needs to get around or is planning to attend the memorial events can do so safely. While we’re planning to run a normal service, there may be short notice changes and diversions as a result of the large number of people travelling and necessary road closures.”