The line had been closed north of Carlisle due to weekend floods. It was submerged under more than two metres of flood water and in places had been covered by mud and debris from landslips.
Acting route managing director Debbie Francis said: “Eight feet of floodwater caused widespread damage to the railway, but work has taken place round-the-clock to make repairs and clear the debris.”
She added: “The orange army has pulled out all the stops to get trains running again and get passengers and businesses on the move. I'd like to thank everyone for their patience during this difficult time. We know that any further rain will simply run off the top of the ground rather than soak in, so we remain on alert to tackle any further problems.”