Virgin Trains bosses this week advised local customers to think ahead about coming bank holiday travel during a capital station closure.
East Coast route commuters, warned of no services to or from Euston on Saturday and Sunday, are asked to plan journeys and reserve seats now in advance.
Network Rail are carrying out HS2 enabling works, expected to disrupt services.
On the regional route, Virgin Trains services between London Kings Cross and Scotland are expected to be extremely popular due to Edinburgh Festival, as well as those seeking alternative routes to and from London.
A spokesperson said: “We expect our services on both routes to be very busy from Friday to Monday. If customers choose to travel, we strongly recommend they book their tickets in advance, make a seat reservation, and allow longer to get to their destination. They should also double check National Rail Enquiries and Virgin Trains websites before travelling.”
Antonia Buckland, high speed rail sponsorship director for Network Rail, added: “The advice to passengers planning travel to or from Euston station this bank holiday is clear - plan your journeys on days other than Saturday and the Sunday and only travel by train on those days if absolutely essential.
"If you do travel, trains will be busier than usual, journeys will take longer and, unless you have reserved one, you won’t be guaranteed a seat".