A storm-damaged rail bridge has reopened after a major project to save it from collapse.

Passenger and freight services resumed over the Lamington Viaduct in South Lanarkshire on Monday morning.

The Victorian structure was severely weakened and left close to falling into the River Clyde after flooding from Storm Frank damaged it on Hogmanay.

Network Rail confirmed on Monday that seven weeks of repairs had been completed earlier than previously thought, ahead of its planned reopening in March.

The train over the newly repaired viaduct was the north-bound Caledonian Sleeper service between London and Inverness at 3am.

Virgin Trains and First TransPennine Express services will also resume throughout Monday.

Phil Verster, managing director of the ScotRail Alliance, said: "I am delighted our engineers have been able to complete this vital job earlier than scheduled and get passengers back onto the West Coast Mainline. We appreciate the understanding customers have shown throughout the recovery operation.

"I am very proud of the hard work and commitment of our engineers who have had to contend with extremely challenging conditions at Lamington, battling against the elements and clock to save this important structure from collapse."

The viaduct’s second pier had been left on the brink of collapse when floodwaters scoured out much of its foundations and hundreds of engineers have been working on it since January to save the structure.

The incident also damaged the second pier’s steel bearings, which support the bridge-deck and track above the pier, a non-load-bearing section of the viaduct’s third pier and the structure’s north abutment.

Over the last seven weeks engineers have placed more than 7000 tons of rock around the battered structure to protect it from the fast-flowing Clyde, constructed concrete supports around the damaged second pier and anchored it to the riverbed using over 100 8m-long steel rods.

Claire Perry, UK government rail minister, said: "When I visited the Lamington Viaduct in January I saw first-hand the scale of the engineering challenge and the dedicated Network Rail team working round-the-clock to resolve the damage.

"In difficult conditions, they have managed to reopen ahead of schedule, and I’m grateful for the patience of customers who were disrupted and to the staff who adapted remarkably.

"We can now get rail customers and rail freight moving again on this vital cross-border rail link, which is the western backbone of the network. Our record investment in the railways continues, along with regular maintenance and inspection, to ensure that they can withstand these unprecedented weather events."