Great Northern rail passengers are set for May Bank Holiday weekend disruption.
Network Rail is closing the Northern City Line between Finsbury Park and Moorgate for three days, and trains between Hertfordshire and the City will be diverted into King's Cross.
Tom Moran, Great Northern and Thameslink managing director, said the project - to replace 45-year-old railway equipment - would reduce disruption on the line.
Mr Moran said: "We expect the new signalling system to significantly reduce the delays caused by signal failures.
"This will benefit our customers but it can’t be done without closing a part of our railway.
"This means we won’t be able to run trains along the route to and from Moorgate this early May Bank Holiday weekend.
"We’re sorry for the inconvenience and encourage passengers to plan ahead and allow extra time for their journeys."
There will be no Great Northern service at Moorgate, Old Street, Highbury and Islington or Drayton Park over the entire weekend (Saturday, April 30 - Monday, May 2).
Once works are complete, a new "digital" signalling system will be in place.
Buses will also replace Great Northern trains between Ely in Cambridgeshire and King's Lynn in Norfolk over the same time period due to engineering work.
Elsewhere on the railways in north London and Hertfordshire, Avanti West Coast and London Northwestern Railway trains between Euston and Milton Keynes Central, via Watford Junction will not run.
London Overground trains between Watford Junction and Willesden Junction are cancelled throughout the weekend, with no Euston to Willesden Junction service after 10am on Saturday and all day on Sunday.
Greater Anglia trains between Liverpool Street and Stansted Airport will not run, and buses will replace trains between Waltham Cross and the airport.
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