Rail passengers who use Euston station to travel to and from London are urged to avoid rail travel for two days over the August bank holiday while work takes place to prepare for the HS2 high speed railway.
No trains will run in or out of Euston on August 26-27 while a major power supply to the station is rerouted by Network Rail.
All services are expected to be extremely busy, with passengers unlikely to get a seat unless they have reserved where possible.
Travellers may also need to change trains, and queuing systems may be in place at busy stations.
Stations affected will include Kings Langley, Hemel Hempstead, Berkhamsted, Tring, Cheddington, Leighton Buzzard, Bletchley, Milton Keynes and Wolverton.
While trains are not running on the West Coast Mainline into Euston, Network Rail will also be completing significant maintenance and improvements elsewhere as part of its national railway upgrade plan.
London Midland spokesman Steve Helfet said: “The bank holiday works will play a key role in providing the infrastructure and capacity to deal with the growing popularity of rail travel.
“As a result of the disruption the advice is, avoid travelling this bank holiday and save your trip to or from London for another day.
“All rail routes between the Midlands and the capital will be busy this weekend.”