People planning to go to London at the weekend from local stations have been advised not to travel by train because of major disruption caused by work on a £1.2 billion upgrade to the line.

People who must travel will have to use a replacement bus services for part of their trip.

Govia Thameslink Railway (GTR), which runs Great Northern services through Huntingdon and St Neots, said Great Northern and Thameslink trains from Peterborough and Cambridge would not run in or out of Kings Cross, St Pancras and Moorgate on Saturday and Sunday (June 20 and 21) while the next stage of the East Coast Upgrade takes place.

GTR, together with Network Rail, is urging passengers not to travel to the capital if possible, with trains from Peterborough and Cambridge, which normally serve the three London destinations, running only as far as Potters Bar where trains will be replaced by buses.

Great Northern is also running a number of shuttle services for connections to London Underground stations. There will also be shuttles between Kings Lynn and Cambridge and on Saturday an hourly service between Ely and Potters Bar.

But GTR is advising passengers from Cambridgeshire to instead use Greater Anglia’s Cambridge to Liverpool Street services for essential journeys to London.

Thameslink’s Peterborough to Horsham and Cambridge to Gatwick airport/Brighton will only operate between Sussex and London Bridge.

The work, being done under strict social distancing rules, involves the future reopening of a disused tunnel into Kings Cross to allow more tracks to be laid so extra trains can enter and exit the station. When combined with other upgrades it will provide greater reliability on services between London, Peterborough and Cambridge.

Jenny Saunders, customer services director for Great Northern and Thameslink, said: “With the vital improvement work Network Rail is carrying out on 20 and 21 June on the East Coast Mainline, we would advise people not to travel at all on this part of the route.

“If you do have to travel on 20 or 21 June, journeys will take significantly longer than usual, so please check ahead at eastcoastupgrade.co.uk, National Rail Enquiries, or the Great Northern or Thameslink websites.”

The Great Northern website is at www.greatnorthernrail.com, and Thameslink’s is at www.thameslinkrailway.com.