Any disruption on the Brighton Main Line could take longer to clear due to three platform closures at London Bridge Station.
The warning comes from Southern’s performance director, David Scorey, who was commenting on the latest phase of works in the £6billion Thameslink Programme.
The improvements, which are due to be completed in 2018, will see more trains with more connections and a bigger station capable of accommodating about 66 per cent more passengers.
In the latest phase of engineering works, platforms 14, 15 and 16 will be closed from May 19, meaning that Southern will be operating from six platforms rather than the current nine.
Mr Scorey said: “It’s fair to say that the remaining platforms will be used to full capacity and if disruption occurs it may take a little more time to recover the timetable.”
Only one Southern service to London Bridge will be diverted by the platform closures – the 7:43am Gatwick Airport to London Bridge service will be diverted to Victoria.
All other Southern services will remain, but passengers are advised to check their train times in the new summer timetable as some services will be re-timed by a few minutes.
The timetable starts from May 19 – the day platforms 14,15, and 16 are closed temporarily.
First Capital Connect’s Brighton to Bedford services will also face changes because of the engineering works but not until December 2014 onwards. From that date, FCC’s services are likely to be diverted along the Elephant and Castle, Herne Hill route to avoid London Bridge while major platform alterations continue.
A spokesman for Network Rail said: “The final station layout will have two dedicated platforms for Thameslink services, enabling 18 trains per hour through London Bridge and six further trains through Elephant and Castle to form 24 trains per hour to travel through central London.”
Southern’s new summer timetable is available at stations and can also be viewed at Southern’s website:
In the timetable, there are additional trains on Sundays from East Grinstead to London Victoria, with a half-hourly service running between 9am and 7pm.