Thousands of Easter train passengers will see their journey times treble as 450 engineering projects delay all main line routes - on one of the biggest ever schedules of weekend works.
The Network Rail projects - 75 more than last Easter - will affect many of the seven million Brits who travel over the holiday weekend from March 25-28.
Delays will hit all six of Britain's main line routes: London to the West, London to Glasgow, London to the Midlands, London to Edinburgh, London to Norwich and
London to Weymouth.
The works will affect 19 of Britain's main 21 rail operators overall.
Passengers will see some journey times treble as they face closed lines, cancelled services and replacement buses.
Holidaymakers planning to jet abroad will also be hit as the Gatwick Express from London Victoria is axed from Good Friday to Easter Monday.
Travel expert Ian Baldry, of IBPTS travel consultants, said: "More engineering works than usual this Easter means more disruption than usual.
"Passengers will be frustrated by works and some leisure travellers will find their journeys confusing.
"And as rail replacement bus staff are often unable to answers questions, passengers will be left even more annoyed."
Bruce Williamson, spokesman for campaign group Railfuture, acknowledged that "engineering works cause inconvenience and customers don't like them" but said that they are a "necessary evil" and have been "overdue for decades."
He told the Telegraph: "Easter is one of the least busy times compared to when commuters are using the trains.
"The works will affect leisure travellers, but there's no other time to do this. There's no time that will inconvenience no one."
He also said it is important the works will finish on time - unlike at Christmas 2014, when 115,000 passengers were hit as works over-ran and Kings Cross and Paddington remained shut.
As part of the projects, Victoria station will be shut to all Southern services.
London-Glasgow services will be slashed or delayed from Friday to Monday, with Crewe to Stafford and Birmingham to Wolverhampton stretches shut.
Birmingham to Crewe will take up to 2hr 10min, double the usual 57min. London to Manchester trips will be delayed 35min.
The London-Edinburgh line will see London-Peterborough take 1hr 46min, double the usual 52min, on Easter Saturday morning and evening and Easter Sunday morning.
Journeys north of Peterborough will be delayed 30min on Saturday and Sunday, with other Virgin Trains East Coast services cut.
Staycationers heading for the south coast from London Waterloo will be stalled by buses from Eastleigh to Bournemouth on Saturday and Sunday, adding 40min to journeys.
Trips on the London-Wales line will be stalled by buses near Cardiff from Saturday evening to Tuesday, and between Reading, Swindon and Oxford on Sunday.
Reading to Swindon will take 1hr 29min, treble the usual 33 minutes.
The London-Norwich line has no services from London Liverpool Street, and buses from Newbury Park as far as Chelmsford.
Among other works, all London Marylebone to Amersham services are axed with Chiltern, lines will be closed in central Manchester, and buses replace trains between Derby and Matlock and Kettering and Corby on Sunday, and from Chester to Northwich all weekend.
The works are part of Network Rail's £40bn railway upgrade plan to provide new station facilities, longer platforms, extra tracks and new junctions.
Network Rail chief executive Mark Carne said: "I'm acutely conscious many people want to use the railway during Easter.
"The vast majority of services will be unaffected, with over 95% of the network open as normal."
Worst affected:
1. London-Glasgow services will be slashed or delayed from Friday to Monday
2. Crewe to Stafford and Birmingham to Wolverhampton stretches will be shut
3. Birmingham to Crewe will take up to two hours and ten minutes, double the usual 57min
4. London to Manchester trips will be delayed 35 minutes
5. Reduced services between Paddington and Reading, and on Heathrow Express
6. No Southern or Gatwick Express services from London Victoria and reduced services on the Brighton
7. Manchester Victoria station closed for nine days from Good Friday, reopening on 4 April
8. Glasgow Queen Street station (high level) closed for 20 weeks from March 20, services diverted to the low-level station or other Glasgow stations
9. Long-distance services through the Stafford area to be diverted via Stoke, with some replaced by buses
10. The London-Edinburgh line will see London-Peterborough take 1hr 46min, double the usual 52 minutes, on Easter Saturday morning and evening and Easter Sunday morning