Work has begun on a vital rail line in London which will disrupt weekend services for 10 months.
Thameslink runs from Bedford to Brighton and Sutton
Thameslink trains will not run into City Thameslink, Moorgate, Farringdon or King's Cross stations on many weekends and on Monday and Tuesday nights.
Between this weekend and July 2004 services running to and from Bedford will begin and end at West Hampstead or Kentish Town.
And trains to and from Brighton and Sutton will begin and terminate their journeys at Blackfriars station.
This is to allow work to begin on a Eurostar station and a Thameslink station at St Pancras.
From September 2004, a concrete enclosure will be constructed underground between the existing King's Cross Thameslink station and St Pancras station.
This enclosure will ultimately house the new Thameslink station to be known as St Pancras - Midland Road.
During this second phase, Thameslink services to and from Bedford will begin and end at St Pancras.
The service to and from Brighton and Sutton will start and terminate at King's Cross Thameslink station.
Mark Causebrook, Thameslink's Managing Director, said: "The work is essential to bring about long term improvements associated with the construction of a new station and Eurostar services running into St Pancras.
"In planning these closures we have all worked together to minimise the impact.
"We have endeavoured to pick times when services are not so heavily used".