Train operator Thameslink has apologised to passengers after a shortage of drivers caused delays and cancellations.
The firm, which took over the Bedford to Brighton service in September, is currently training 62 new drivers and recruiting a further 89 to fill the void.
Those currently training will finish their courses between now and August
A Thameslink spokesman said: “We would like to apologise for service levels. We appreciate that recent weeks have been a difficult and sometimes frustrating time for many of our passengers and we are sorry if you have been personally affected by delayed and cancelled services.
“When we took over the franchise in September we knew that punctuality and reliability on the Thameslink route in particular had been declining for the past three years.
“We immediately put plans in place to address the underlying issues but knew that the changes we are making will take time to deliver their full results.”
Shortages are covered by current train drivers volunteering to do overtime but the problem is exacerbated by the need for essential training for the new routes drivers will be taking into and around London Bridge, plus a conversion course for driving new trains.
It is expected that driver-related cancellations will reduce in January.