Rail users have been warned of travel disruption over Easter with lines being shut in many areas.
Major engineering projects include the Reading station redevelopment and line improvements between London Euston and Watford Junction.
Southeastern services to Sussex and Kent will also undergo changes.
Network Rail says it has contingency plans to prevent a repeat of delays caused by overrunning works at Christmas.
On 27 December, King's Cross station was shut and Paddington was closed for part of the day after engineering works took longer than expected.
There were also chaotic scenes at Finsbury Park in north London, which became so crowded that arriving passengers were unable to get off trains.
Network Rail Chief Executive, Mark Carne, said: "We have thoroughly reviewed our Easter improvement work and worked closely with the train operating companies.
"The industry has good contingency plans in place that will put passengers first."
Dorking in Surrey and Crewe in Cheshire will be among the areas affected over the bank holiday weekend, as will the lines between Lancaster and Carlisle and Peterborough and Ely.
Engineering work in the Shenfield area of Essex will affect routes from London Liverpool Street to Norwich in Norfolk and Southend in Essex.
Between Friday 3 and Monday 6 April and on Sunday 12 April the railway between Hayes & Harlington in West London and Didcot Parkway in Oxfordshire will be closed while further work is carried out on the Crossrail project.
Mr Carne said: "We are acutely conscious that many people want to use the railway during the holidays to reunite with their friends and families, which is why the vast majority of the network is running normally over the holiday period, but there will be disruption for some."