A major line upgrade means trains from Peterborough and Cambridge will not run into King’s Cross, Moorgate or St Pancras this weekend.

On June 20 and 21 passengers are urged not to travel, as the latest phase of the £1.2 billion East Coast Upgrade by Network Rail takes place.

Trains from Peterborough and Cambridge that normally serve Kings Cross, St Pancras or Moorgate will run only as far as Potters Bar, from where replacement bus services will operate.

The Saturday service between Royston and King’s Cross will not run.

Great Northern will run shuttle services between Welwyn Garden City and New Barnet, and between Stevenage and Gordon Hill, for connections via replacement bus services to London Underground stations.

Early on the Sunday morning, buses will replace trains between Stevenage and Gordon Hill.

On the Saturday only, there will also be an hourly service between Ely and Potters Bar.

However, anyone making an essential journey between London and Cambridgeshire or Norfolk is advised to use Greater Anglia’s Cambridge to Liverpool Street services if they have no alternative.

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

Thameslink services between Bedford, London and Brighton via St Pancras will run as normal, except for Sunday services on the St Albans – Sutton route, which will run only between St Albans and St Pancras.

People whose journeys are really necessary, with no other way to travel between Peterborough/Cambridge and South London, Surrey or Sussex, are advised to use the replacement bus service between Potters Bar and St Albans.

Over the weekend, Network Rail will be installing new overhead line equipment, the latest stage of a £1.2 billion project that will eventually see a disused railway tunnel leading to King’s Cross reopened, allowing additional tracks to be laid so more trains can enter and exit the station. When combined with upgrades elsewhere on the route, the East Coast Upgrade will enable more reliable journeys between London, Peterborough and Cambridge.

All the work is being done under strict social distancing rules.

Jenny Saunders, customer services director for Great Northern and Thameslink, said: “In response to the coronavirus pandemic and the need to maintain space on board for social distancing, we are already asking people to wear a face covering, avoid the busiest times of the day and think, ‘Is my journey necessary? Can I travel another way?’

“With the vital improvement work Network Rail is carrying out on June 20 and 21 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 those days, 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.”

Ed Akers, principal programme sponsor for Network Rail, said: “The COVID-19 crisis continues to bring significant challenges for the railway. However, we are working day and night to keep the railway running reliably and safely and to carry out essential work.

“On Saturday 20 and Sunday 21 June, we will continue with the vital £1.2 billion East Coast Upgrade programme. We’ve changed our working methods on site to make sure we can follow public health guidelines and carry on with this project, which will bring significant benefits for passengers.”