Rail users have been warned of major delays over Easter as a main route between London and the West Midlands will be closed for maintenance work.
London Midland advised passengers to postpone travelling between Hemel Hempstead and London Euston during work on the West Coast main line.
The operator said it was part of Network Rail's £81m plan to replace nine miles of track, signalling equipment and overhead power lines.
It apologised for the disruption.
Passenger groups urged train companies to keep rail users informed.
'Longer journey times'
Network Rail said the work would allow Orphanage Road bridge at Watford to be replaced over Easter.
London Midland said the work had been postponed because a 350,000 tonne landslide had blocked the Chiltern line.
Passengers are being urged to check services before travelling as bus replacements and diversions will be in place on some routes.
It said passengers should be prepared for busier services and longer journey times.
Terry Oliver, from London Midland, said: "My advice to passengers would be to postpone travel to another date if possible.
"Journeys will involve changes and will take much longer than normal."
Virgin Trains advised people to avoid travelling on the route between Birmingham and London.
It said passengers would also be able to use tickets on the Chiltern Line, where extra services have been laid on.
London Midland said no trains would run between Bescot Stadium and Rugeley Trent Valley until Wednesday because of separate electrification work.
Phil Davis, from TravelWatch West Midlands, said: "They want to do these jobs during the holidays but it's not always ideal.
"Getting information to passengers is key so people travelling from Birmingham can make alternative arrangements."
The Watford closure is the sixth of eight Network Rail has scheduled for the work.
A number of projects will take place over the Easter break, including the Reading station redevelopment, a closure of the line between Hayes & Harlington in West London and Didcot Parkway in Oxfordshire while further work is carried out on the Crossrail project