Transport bosses have confirmed that extra train services will be running for people travelling to London to pay respects to the Queen.
A limited service will run through the night on some routes.
Demand is expected to be particularly heavy from Wednesday, when the public can attend the lying-in-state at Westminster Hall from 17:00 BST.
The Rail Delivery Group said it was doing “all it can” to ensure smooth journeys during the period of mourning.
The Queen, who died on Thursday aged 96, will lie in state in Westminster Hall for four full days before her funeral, meaning the public will be allowed to view her coffin.
Hundreds of thousands, if not millions, are expected to travel to the capital.
‘Check before you travel’
Only a handful of operators will be putting on night trains and they are expected to be very limited.
For example, there will be an extra train per hour on some routes, and every two hours on some others.
Avanti West Coast, which is still running a dramatically reduced timetable amid a staff shortage, will put on some more train services this week to help people travel to the capital.
Services on Avanti’s busiest route between Manchester and London are currently reduced to one per hour.
From Tuesday until Thursday, between 9.35am and 5.55pm there will be four further trains from Manchester to London Euston, and four extra trains north from London to Manchester between 12.40pm and 8.40pm.
On Friday, Avanti will be running three extra trains each way, between the same times.
The Rail Delivery Group, which represents train companies, told customers to check journey planners for the most up-to-date information.
It also warned that services to, and stations in, London would be “extremely busy” as a result and has urged passengers to leave plenty of time for travel during the official mourning period, which ends the day of the Queen’s state funeral on Monday 19 September.
Transport for London (TfL) and Network Rail said there were plans to ensure people could travel “as easily as possible”.
“The transport industry is working hard to help people pay their respects in London and across the UK,” said Sir Peter Hendy, chair of Network Rail.
“Please make sure you check before you travel as we expect the road and transport networks to be busy.”
Network Rail said a normal timetable would be running on the day of the funeral, rather than a reduced one that might operate on a regular bank holiday, along with some additional services.
Andy Byford, TfL’s transport commissioner, said that while normal services were scheduled on the London Underground, “there may be short notice changes and diversions as a result of the large number of people travelling and necessary road closures”.
Some underground stations will be busier than normal, TfL said, with some disruption expected due to some stations being temporarily closed, or normal routes in and around stations being changed.
People have been told to avoid Green Park tube station if possible, and to use others such as Victoria, Piccadilly Circus and St James’ Park.
The Elizabeth Line does not usually operate any services on a Sunday on the central section between Paddington and Abbey Wood, but this Sunday it will operate 12 trains an hour.
Some bus services will be diverted because of road closures, including night buses, and some taxi ranks will be closed as cabs and coaches will be affected by road closures.
National Express said London Victoria Coach station will be closed on 19 September. All of its London services will be diverted via Wembley Stadium, with the exception of journeys between London and Dover, Ramsgate and Luton and Stansted Airports. These services will be diverted via Stratford and Baker Street instead.
For those travelling from further afield, Heathrow Airport has said some flights will be disrupted on Friday.
Journeys could be cancelled or rescheduled in order to ensure silence over central London as the Queen’s coffin is moved to Westminster Hall.
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