Transport Secretary Patrick McLoughlin formally opened a purpose-built train depot in Three Bridges last week as part of the Thameslink Programme, which will see 60 per cent more carriages and 50 per cent more seats running out of St Albans by 2018.

Mr McLoughlin said: “Our plan for passengers is delivering real improvements for those who use Thameslink services. The opening of this state-of-the-art facility is a major milestone and paves the way for an impressive new fleet of hi-tech trains to come into service from spring next year.”

Commenting on Labour leader Jeremy Corbyn’s plan to nationalise the railways, Mr McLoughlin also said: “Those people who have got rose-tinted glasses for a nationalised railway have forgotten just how desperate the service was when it was nationalised.”

Journalists, investors and executives were taken on a tour of the facility and walked the full length of the brand-new trains, which have a number of additiional features designed to cope with the increasing demands of both long- and short-distance commuting.

Iain Smith, the programme director for Govia Thameslink Railway (GTR) told reporters that the £300 million project would see the introduction of 115 new trains - 55 12-carriage and 60 eight-carriage trains.

Mr Smith said: “We’re looking at 1,754 passengers per 12-car vehicle. It’s an interesting comparison if you look at the Eurostar trains, which we’re also building; they only take 900 people and they’re 400 metres long as opposed to the 240 metres for these trains.”

Matthew Streeton, who is responsible for information systems as GTR, explained that the new carriages are able to weigh themselves and give passengers live information about where there might be more space.

He said: “Each carriage is able to weigh itself and it assumes 80kg per passenger. The system is then able to determine whether it’s half-full, completely empty or whatever. It then feeds that information, in real time, to the customer.”

Despite a lower seat-density per carriage on the new trains, the increased frequency of much larger trains will mean that more seats and more space will be available, according to customer operations manager Lee Millard.

He said: “It’s been a very difficult train to design because it has to cater for a mixed bag of needs and has to be able to do it very quickly.

“It’s a massively busy route; we desperately needed more space. Through central London you’ve got a very high frequency service required. We needed bigger doors; we needed it to be much easier to get on and off.”

The first wave of new Class 700 trains are due to start service in the spring with the project due for completion in 2018.