The two rail companies which operate in Stevenage and North Herts are investing millions of pounds to upgrade their fleets of trains – which are among the oldest in the UK.

A survey has revealed that the average of age Virgin Trains East Coast stock was 29.3 years – the third highest – while Govia Thameslink Railway followed in fourth with an average of 28.9 years.

Merseyrail topped the poll with a 36.3 average, while London Overground’s 4.7 was the lowest.

In response, a Virgin Trains spokesman said: “We are investing £140 million in improvements over the lifetime of the franchise which we took over in March this year.

“Last week we announced a £16m contract to fit 35 newly refurbished diesel engines on our oldest fleet, our high speed trains. The introduction of 65 new Super Express trains from 2018 will replace our current fleet.”

A spokesman for Great Northern, which operates Govia trains which travel through the likes of Letchworth, Hitchin and Stevenage to London King’s Cross, said: “We started our franchise just over a year ago and already we’ve brought in the first of four brand new fleets of train on to our network, on the Thameslink route.

“The Class 365 trains we use on the King’s Lynn and Cambridge express services are only mid-life and these are being put through a £31m refurbishment programme which also includes adding new passenger information systems and features for disabled passengers.

“But even these will be replaced next year by newer, air-conditioned Class 377 Electrostar trains which is also when the older Class 317s and 321s – mostly used in peak times for extra capacity – will be replaced as we introduce Britain’s biggest order of new rolling stock with 1,140 Class 700 carriages to give passengers direct services from Cambridge to Gatwick in an hour and 40 minutes.”