It was not possible to carry out the coffee-spillage test as Britain’s fastest domestic train shot through the Kent countryside at 140mph.

Southeastern is providing neither buffet nor trolley service on its new high-speed service because it says passengers would not have time to finish their drinks before arriving at their destinations.

But it is fair to say that the train would nearly have passed the test.

Today’s 31-minute test ride from London St Pancras to Ashford — a journey that normally takes more than twice as long — was extremely smooth for the first 29 minutes. Then we lurched off High Speed One, Britain’s only TGV-standard track, and on to the old conventional railway for the final mile.

LNER's Mallard breaks speed record, 1938

While the record was being made tea was being served and the motion was so smooth none was spilled

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Had I been holding a coffee, it would have ended up all over my cream trousers.

This is the strange combination of 21st-century precision engineering and early Victorian rail standards that passengers will experience when a limited commercial service starts on June 29.

They will have to pay a premium of up to 34 per cent to use the bullet-nosed trains but only part of the journey will be on high-speed track shared with Eurostar.

Passengers from Ashford and Folkestone will save about 40 minutes but those from Faversham will spend most of their journeys on 150-year-old lines and save only 7 minutes.

From the outside, the Japanese-built train looks sleek and streamlined but inside it is no different from any other modern commuter train. There is plenty of legroom but no added luxuries, not even a first-class carriage.

Directors will have to share space with their workers, though there should be plenty of seats for everyone. Not only is it the worst time to start a new service, but many existing Kent commuters will prefer to continue catching slow trains to Charing Cross or Cannon Street than have to change on to the Tube at King’s Cross.

Commuters from Kent to Canary Wharf will save up to an hour a day from December when Southeastern’s trains start calling at Stratford.

The company describes its new 140mph service as “high speed” even though in the rest of Europe the definition of high speed is 300km/h or 186mph.

Eurostar trains do travel at 186mph on High Speed One but the new Kent commuter trains were designed with a top speed of 140mph because they will spend so much time on conventional tracks where the maximum limit is 100mph.

Being much lighter and shorter, they accelerate faster than a Eurostar, however, and therefore will not hold up the international trains.

The greatest time-savings for the new service are likely to be for those who currently drive into London from Kent. Rather than crawling for the last 20 miles, they will be able to use the new park-and-ride station at Ebbsfleet and catch one of 12 trains an hour taking only 17 minutes to St Pancras.

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