The omens looked good for a day of rail buffery when my train from Oxford passed Richard Trevithick at Reading and then drew up alongside Isambard Kingdom Brunel at Paddington. The first was an aging class 37 diesel engine whose name celebrates the builder of the earliest working railway steam locomotive. The second is a newer (but still quite old) HST power car named in honour of the man many consider the greatest engineer who ever lived. His achievements included, of course, not only the design of Paddington itself but most of the straight and level tracks I had just travelled over to reach it.

Today, though, I was off to appraise the work of another eminent Victorian, William Barlow, as it can be seen at St Pancras - now gloriously restored, at a cost of £800m, to serve the needs of the 21st century and beyond. As consulting engineer for the Midland Railway, he designed one of the wonders of the world. His magnificent train shed was at the time of its construction (1867) the widest single-span structure on the planet, 245ft 6in from side to side, enough to accommodate (eventually) seven platforms and with no descending pillars to mar the beauty of the arch.

Incredible as it seems now, both this fine shed and George Gilbert Scott's neo-Gothic hotel to which it is attached were threatened with demolition in 1966 by British Rail executives who failed to understand their value. John Betjeman worked indefatigably (with others) to persuade them they were mistaken. Very properly, Sir John - in a fine sculpture by the Woodstock artist Martin Jennnings - now occupies a prominent place in the refurbished station. I could not resist having my photograph taken with him last week - as so many thousands of other people will in the years ahead. What a pity, I thought, that I could not take him by the hand and lead him towards the champagne bar - the world's longest - for a glass of his favourite bubbly.

Sir John wrote of the departure from St Pancras as it was in steam days, when travellers passed through a succession of tunnels: Rumbling under blackened girders, Midland bound for Cricklewood Puffed its sulphur to the sunset where that land of laundries stood.

But it is other of his lines, perhaps with more appropriate connections with Continental travel, that Martin chose to carve in stone close to the statue: Here where the cliffs alone prevail I stand exultant, neutral, free, And from the cushion of the gale Behold a huge consoling sea.

The sea, strangely, is something you never get to see, even from far away, on a journey through the Channel Tunnel. I mentioned this in the article I wrote after travelling on one of the first Eurostar services to Paris when they began 13 years ago. This was a press trip, during which I had the thrill of riding in the driver's cab as we raced through the French countryside at 180mph. The press once again travelled in considerable numbers on Wednesday of last week when the new service began from St Pancras. The Oxford Times's deadlines meant I could not be among them, but Eurostar's publicity department kindly arranged for me to visit Paris the following day to sample the fastest rail journey yet possible between the capitals.

As is so often the case on an early morning train from Oxford, there was standing room only on The Cathedrals Express. The service ran on time, however, and after a speedy trip on the Circle Line I was at St Pancras with more than an hour to spare before the departure of my 11.05 train to Paris. Much of this I spent in awestruck admiration of the station. I chose (but of course!) the champagne bar from which to survey Barlow's magnificent structure, with its pale-blue girders and acres of "sun-comprehending glass" (as Philip Larkin wrote in another context). Around me people were knocking back glasses of fizz, priced upwards from £7.50 and including Dom Perignon at £25. The £12.50 Bollinger had all gone - quite a run on it the day before. I stuck to coffee in a rare moment of self-control, partly explained by the fact that I had been drinking champagne the night before at the opening party for Eight at the Thatch in Thame. (Please don't shop me to Dawn Primarolo.) Thirty minutes before departure, I was obliged to check in and pass through security and passport control - UK and French. Then there was a 20-minute wait in the departure lounge, which has been fashioned from the column-filled space beneath the platforms originally designed for the storage of barrels of Burton-brewed beer. The clutter of bodies and luggage bathed in garish fluorescent light made this the least attractive aspect of the St Pancras experience.

Once on the train, however, there was plenty of room to stretch my legs. Though I was travelling Standard, for the first time on Eurostar, I found the seating well-planned and comfortable. With no other passengers in my section of the carriage (though the 18-coach train was otherwise pretty full), I was able to move about, enjoying the views from both sides. These included (once the tunnels under London were passed) a fine sight of Rainham Marshes - frost glistening in the autumn sunshine - as we sped at the maximum 186mph towards the coast. Far ahead of us in the distance, at one point, I noticed a curious Phileas Fogg-style balloon. What I suspected might have been a slow-speed service to the Continent turned out to be an advertising marker over Leeds Castle.

Our smooth running was testament to the excellent engineering that went into the $6bn high-speed line. On the other side of the Channel (after 20 minutes in the tunnel) there were times when the ride was much less even. One particularly sharp lurch sent flying the mini-bottle of claret I was enjoying as part of my bought-from-the-bar lunch (pasta, with mushrooms, chestnuts and cream, for less than a fiver). A colleague who knows about these things tells me the line has become another 'victim', in places, of the trench warfare of 1914-8.

The trip took exactly the 2hr 15min promised in the adverts. The same was true on the the return journey, on which I embarked after barely time for a quick stroll in the sunshine around the Gare du Nord. This is a wonderful service which makes quite possible - no, really rather easy - a day trip to Paris for shopping, lunch, gallery-visiting or any of the other activities for which Paris is (in)famous. Take my advice: try it.

Finally, having begun this article with the subject of locomotive names, I shall end with it too. It has long seemed to me a pity that the mighty machines that propel us to the Continent carry only unmemorable numbers. With the new services so much in the public eye, perhaps it is time for a change. True, the Midland Railway, which built St Pancras, had no time for names, bestowing only two, I believe, on locomotives it owned (which it always insisted on calling 'engines'). But things changed once it became part of the London, Midland & Scottish Railway after 1923. How stirring were the names carried, for instance, by some of Sir William Stanier's 'Jubilee' class, which were still hauling the bulk of the fast trains from St Pancras (as I remember) into the 1960s. Wouldn't it be good to see again a sleek express headed by Thunderer, Glorious, Colossus or Bellerophon?