Rail services from a major London station will be disrupted due to engineering works this Christmas.
Thameslink is reminding travellers to plan and check for alternative routes during this period.
Network Rail has announced that from December 21 to December 29, there will be no East Midlands Railway services to Bedford, or Thameslink services between St Pancras and Harpenden.
It says this is due to essential upgrades aimed at improving the reliability of the rail network for years to come.
The upgrades are part of a programme to allow East Midlands Railway (EMR) to run its new fleet of bi-mode trains at speeds of up to 125mph in the future.
This will result in smoother and faster journeys for passengers travelling to and from the East Midlands and London.
Because of the work, a section of the Midland Main Line between London St Pancras and Harpenden will be closed for nine consecutive days.
During this time, Network Rail teams will be working on improvements including upgrading the overhead lines, replacing a bridge deck at Agar Grove in Camden, and installing a new bridge under the railway to provide access to Radlett Strategic Freight interchange.
Daniel Matthews, head of operations delivery for Network Rail, said: "We would like to apologise to passengers who will be impacted by this vital work over the festive period.
"This work is essential, and it will mean smoother, faster, and more reliable journeys for customers."
Passengers travelling between London St Pancras and destinations on the Midland Main Line, including Luton Airport Parkway, St Albans, Bedford, Nottingham, Derby, and Sheffield, should expect longer journeys and rail replacement buses.
There will also be no Thameslink train services between London St Pancras and London Bridge from Friday, December 27 to Sunday, December 29, as engineering work will be taking place to upgrade the tracks.
Jenny Saunders, customer service director for Govia Thameslink Railway, said: "We know how important this time of the year is to our customers, which is why, with such a lengthy period of improvement work planned over the festive period, we want to give them as much time as possible to plan ahead."
Philippa Cresswell, customer service director for East Midlands Railway, added: "We are working closely with Network Rail and other operators to keep customers moving throughout the festive period; however, journey times will be significantly longer than normal, with rail replacement buses and amended timetables in place."
Passengers are urged to check National Rail Enquiries before they travel, as well as EMR’s and Thameslink’s websites and social media channels.
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