The December timetable change for Great Northern services has been cancelled – meaning, among other things, that trains between Stevenage and Hertford will run for an extra six months.

A wholesale timetable change has caused chaos on the railways since May 20. Rail industry bosses announced yesterday that as part of efforts to sort things out, there would be no winter schedule this year for eight line operators – including Govia Thameslink, which runs Great Northern.

One of the consequences of this is that a temporary bus replacement period of about 18 months – on the Hertford loop between Stevenage, Watton-at-Stone and Hertford North – will be pushed back by half a year.

Govia Thameslink told this paper this was because the postponed timetable change meant there would still be sufficient capacity at Stevenage to run services to Hertford.

The bus replacement period, necessary because of delays building a fifth platform at Stevenage, had been set to last from December 2018 until at least 2020. It will now start in May 2019.

Great Northern is already set to introduce a new timetable on Sunday, in an attempt to stabilise services that have been crippled by near-constant delays, cancellations and overcrowding.

The decision not to change timetable on December 9 comes after Network Rail chief executive Andrew Haines reviewed the plans at the request of Transport Secretary Chris Grayling and Network Rail chairman Sir Peter Hendy.

Sir Peter said: “The railway industry has taken a long hard look at its plans for the next timetable change in December and, taking into account recent painful lessons, the industry has scaled back its ambition and tempered it with a more cautious, phased approach to introducing the new timetable.

“While there will still be new services introduced this December, other new services will now be introduced more gradually over the next few timetable changes to help smooth their introduction and maintain a reliable service for passengers and businesses alike.”

Rail Delivery Group chairman Paul Plummer added: “Many people have suffered unacceptable disruption following the introduction of the new timetable in May, for which we are sincerely sorry. The industry is determined to learn the lessons from what went wrong.”

The other seven operators that will not introduce December timetables are Northern, CrossCountry, Great Western, London Overground, South Western, TransPennine Express and West Midlands Trains.