First Capital Connect ran an emergency timetable after severe rail disruptions on Tuesday (December 17).
Passengers were also advised to find alternative routes home from London Kings Cross to Biggleswade, Sandy and Arlesey after major delays occurred throughout the day.
The problems started after a fault developed in the signalling system in London.
The train company lifted the usual restrictions on peak time travel and declassifed first class, also increasing its normal compensation offers.
Keith Jipps, customer service director for First Capital Connect said: “After Network Rail fixed the signalling fault we pulled out all the stops to put our trains back in position overnight and gave our passengers a full service again on Wednesday morning.”