South West Trains said services between Wimbledon and Waterloo will be delayed or even cancelled as emergency engineering works continue today.
Emergency engineering work in the Wimbledon area is causing disuptions to services in and out of central London and the rail operator said this is expected to continue until 4pm.
It follows considerable delays earlier today when services were held up by as much as an hour, for which South West Trains apologised.
In a statement, the company said: "Services arriving at and leaving London Waterloo are returning to normal.
"By 2.30pm the full weekday timetable will resume with trains calling at all normal stations.
"Some long distance services between London and the West of England/South Coast may be delayed after 2.30pm due to length of time these trains take to complete their journey.
"A normal weekday service will operate from London Waterloo this Evening.
"We thank you for your patience whilst this problem was fixed and are very sorry for the disruption to your journey this morning."