Rail passengers face ten months of disruption as engineering work starts this month on the Thameslink service between Brighton and Bedford.

The work, needed to prepare for the new Thameslink station at St Pancras and its Channel rail link, will spell misery for many train users.

Thameslink trains will not run through London. Services starting in Brighton will stop at London Bridge or Blackfriars.

A spokesman said the work would be carried out at weekends and late evenings to cause minimum disruption to commuters.

The first stage of track and signalling improvements by Network Rail will take place between 2am on Saturdays and 5am on Mondays, and after 9pm on Mondays and Tuesdays, finishing at 5am the next day.

It starts on September 27 and is expected to last until mid-December.

The second stage will start in 2004 and work is due to end next July Services running to and from Bedford will start and terminate at West Hampstead or Kentish Town.

There will be no services stopping at Moorgate, Farringdon or Kings Cross Thameslink stations in either direction from later this month until Christmas.

In September 2004, after the initial track preparation and signalling work is finished, the Thameslink route from Brighton to London will run to Kings Cross.

Passengers will have to cross to St Pancras to continue to Bedford.

This stage is expected to last for about six months while an underground enclosure to house the new Thameslink station at St Pancras is built.

A Thameslink spokesman said: "Although we understand it is going to inconvenience people, there is help at hand in order for them to be able to continue their journeys across central London."

All work is expected to be completed by April 2005 and the route through London reopened.

Advice on alternative routes will be available at stations and at www.thameslink.co.uk/allchange