Engineers are cramming a more than 100 nights work into five days to flood-proof a Victorian railway tunnel near Northampton
Crick Tunnel will be closed from Monday (March 15) while the work is carried out with buses shuttling passengers between Castle station, Long Buckby and Rugby.
Problems with water seeping into the 140-year-old tunnel cost passenger and freight trains using the route a total of 250 hours delays between 2012 and 2020.
Work to renovate brickwork, drainage and track bed would normally have meant it being closed overnight every night for a year and cost around £11 million.
But condensing the work into a few days while the Covid-19 pandemic is keeping passenger numbers low will take £7.5million off the cost.
James Dean, Network Rail West Coast Mainline South route director, said:“This speedy upgrade of Crick tunnel shows how the rail industry is coming together to get the West Coast main line in the best possible shape for passengers when they can return once coronavirus travel restrictions are eased.
"This is all part of our commitment to build back better as the country emerges from the pandemic.
"However, as the line will need to close for the major upgrade, I’d urge anyone still making essential journeys to check National Rail Enquiries, so they know what to expect when they travel.”
Next week's closure is believed to be the longest since the tunnel was built in 1881 as part of the Northampton loop, connecting the town to the West Coast Main Line.
London Northwestern Railway, which operates services on the line between Northampton and Birmingham, admit the work will be an inconvenience for some.
LNR's customer experience director, Lawrence Bowman, said: “I thank our passengers making essential journeys for their patience while Network Rail carries out these important improvements to the railway.
"I urge our customers to plan ahead and check their train times before setting out if they plan to travel during the work.
"Replacement buses will be in operation between Northampton, Long Buckby and Rugby for those who need them.”
Engineers carried out similar work on the 1½-mile long Kilsby Tunnel during last year's first lockdown.