Train passengers travelling between Portsmouth and London have been warned to expect major disruption to services while upgrades are made to the railway.
Network Rail and South West Trains have published new train service information for passengers ahead of the work at London Waterloo station between August 5-28.
During this time less services are expected to run across the network, while some smaller stations may have to close temporarily.
The work will include extending platforms 1-4 for longer trains on suburban routes.
Platforms 1-9 will be closed while work is going on, but platforms 20-24 will temporarily reopen.
This is part of the £800 million Waterloo & South West upgrade, which the companies say will provide 30 per cent more space on trains during the busiest parts of the day.
What does this mean for Portsmouth passengers?
Fewer trains will call at stations in the Portsmouth area while work is going on between August 5-28.
This means some trains may not be running, services will be busier than normal, and journeys may take longer.
Both companies are encouraging people to travel either later or earlier than they normally would, or consider working from home or planning a summer holiday.
What do the companies say?
Christian Roth, managing director of South West Trains, said: ‘This is the biggest investment in this railway for decades and it will provide a significant increase in capacity for the thousands of passengers who use this railway every day.
‘There will be some short term changes and disruption for passengers, particularly during August.
‘That is why we are doing everything we can to inform passengers and businesses well in advance so they can plan their journey and understand the possible impacts.’
And Becky Lumlock, route managing director at Network Rail, said: ‘This [upgrade] means big changes for passengers and we want them to be well-equipped to plan ahead.
‘Fewer trains will be arriving and departing at Waterloo, and some stations will close entirely.
‘This is why we’re asking passengers to check how they will be affected now so that they can plan ahead, either by planning to travel at different times of day or working from home on some days during the works.
‘Waterloo is already the busiest railway station in Britain by a significant margin and passenger numbers are continuing to grow. We therefore need to make these upgrades to increase capacity now.’
To find out more about the upgrades go to southwesttrains.co.uk/wswupgrade.