Building work will begin next month on a new station for Thameslink at St Pancras in London.
Work on the new station is due to begin on 11 September
During the construction Thameslink trains from Bedford will finish at St Pancras while services beginning at Brighton will end at King's Cross.
Tube services will not be directly affected by the works but passengers may find that the pattern of their journeys will change.
Work is due to commence on 11 September until mid May 2005.
'Regeneration of area'
Some trains on the Wimbledon loop will terminate at Blackfriars.
Transport for London said the split Thameslink service means there will be extra passengers walking between King's Cross Thameslink and St Pancras.
Camden Council will provide marshals to direct people walking.
Mike Brown, London Underground's chief operating officer said: "The new Thameslink station at St Pancras will be a welcome addition to the regeneration of the area's railway infrastructure.
"Thameslink has consulted with rail industry partners, including TfL, to ensure that the inevitable disruption caused by the construction works can be kept to a minimum and that travellers can complete their journeys safely."