Commuters face severe rail disruption after almost half of the platforms at the UK's busiest train station closed for a major overhaul.
Workers heading for London have been told to expect reduced services on the first working day since platforms one to nine at Waterloo were closed on Saturday until August 28 to enable engineering works to take place.
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South West Trains have warned passengers stations such as Vauxhall, Clapham Junction, Woking and Guildford will be "exceptionally busy" as they will have fewer services running and customers could be forced to queue to get in.
Seven stations in south west London will be closed during the works, according to Network Rail's website.
An average of 270,000 journeys are normally made to or from Waterloo every day.
The project to extend the station's platforms will allow longer trains to operate on suburban routes from December and provide space for 30% more passengers at peak times, Network Rail said.
To ease some of the impact of the work the old Eurostar platforms are being used at Waterloo for the first time since the cross-Channel train service relocated to London St Pancras in 2007.
Rail chiefs urged passengers to consider taking a holiday, working from home or travelling earlier or later than normal while the project is under way.
But businesses leaders said this was not always possible, and the Federation of Small Businesses warned traders will suffer lost income they will be unable to recover even once the work is completed.
Network Rail chief executive Mark Carne has previously admitted he is "worried there will be challenging days" and accepted that "there are going to be days when the service is very difficult for people".
First Group and Hong Kong-based MTR will take over the South West Trains franchise from Stagecoach on August 20.
The Waterloo work will culminate over the August bank holiday weekend, when it will be one of a number of large projects being carried out.
Passengers hoping to take a leisure trip on the final public holiday before Christmas will find major changes to services out of London Bridge, London Euston, London Liverpool Street and London Paddington, as well as Waterloo.
The work at Euston will be one of the first major physical projects in preparation for the HS2 high-speed railway, as a new power supply is installed at the station.