Hundreds of Network Rail staff worked through Sunday night to respond to damage caused by the severe storm that swept across the south of England.
More than 200 trees fell onto the network overnight; power lines were damaged; and a landslip occurred in the New Forest.
There were also problems with signalling and other equipment resulting from power cuts caused by the storm.
This meant that many lines into London were suspended as commuters arrived at stations for the Monday morning rush hour.
Network Rail managing director of network operations Robin Gisby said on Monday:
“Network Rail is dealing with this severe weather in exactly the way that we and the train operators planned over the weekend.
“We have had several hundred staff on duty through the night and into the morning to monitor conditions and react to any damage or disruption.”