Rail firms have repeated warnings to passengers travelling over the bank holiday weekend with major engineering work affecting several lines.
Virgin Trains says services will be extremely busy over the long weekend.
High demand is expected for east coast trains between London King's Cross and Scotland due to passengers seeking alternative routes to and from London because of the closure of London Euston on Saturday and Sunday, as well as Edinburgh's festivals coming to an end.
London Waterloo services - which have been disrupted for more than a fortnight as part of a major project - have been reduced even further until Tuesday.
Fewer than half of normal weekday services will operate as platforms 1-14 are closed to enable platforms to be extended to accommodate longer trains, boosting capacity at the UK's busiest station by 30%.
National Express is putting on an extra 4,000 seats over the weekend to destinations affected by the Euston and Waterloo work.
Between Saturday and September 2 there will be no Southeastern services to or from London Bridge, Waterloo East and Charing Cross as work continues to rebuild London Bridge and the surrounding railway.
Queuing systems will be in place at Cannon Street station between Tuesday and Friday next week to cope with demand.
Due to Crossrail work there are no trains between London Liverpool Street and Shenfield, Ingatestone, Billericay and Barking on Sunday and Monday.