For today's West Coast Main Line travellers, having circumnaviated the beggars and rough sleepers, the Euston Experience consists mainly of milling around a large, characterless concourse, distinguished only by its minimal seating and constantly proliferating franchise outlets. But it was not always thus.

Around 150 years ago the Euston terminus was possibly the most majestic railway building on the planet, the concourse equivalent being its elaborately decorated Great Hall designed in classical Roman style by the architect, Philip Charles Hardwick. More splendid still, though, was the station's entrance, the earlier creation of Philip Charles' father, Sir Philip Hardwick.

It became universally known as the Euston Arch, but it was not technically an arch at all. Rather, it was a Greek propylaeum: a ceremonial gateway, the largest ever built, modelled on the entrance to the Acropolis in Athens - only the finest gateway of the ancient world being judged symbolically appropriate for such an amazing achievement of the modern world as the first long-distance railway.

Flanked originally by four cubical lodges and two hotels, its most striking features were its four massive Doric columns, 45 feet high, crowned by a frieze and architrave on which was proudly and loudly emblazoned the single word: EUSTON.

Hardwick's masterwork, completed shortly before the first official London to Birmingham train in September 1838, cost the London and Birmingham Railway Company an eye-watering £35,000 (£2.3 million in today's money).

The entrance to the London passenger station - opening immediately upon what will become the Grand Avenue for travelling between the Midland and Northern parts of the Kingdom - the directors thought that it should receive some embellishment. Some embellishment indeed.

The first journeys up the Grand Avenue took Birmingham passengers over five hours, even when there weren't leaves on the line, as the trains lacked the power to ascend the steep incline between Euston and Camden Town and had to be drawn up on a fixed winding cable. The reverse trip was equally hazardous, as the engines were simply detached at Camden, leaving the carriages to run down the hill into the station, controlled only by a brakeman.

The Birmingham journey terminated, of course, at Curzon Street Station; I say 'of course' because many readers will surely have noted the close resemblance between the Euston Arch and the Birmingham station, or at least its gateway and booking office, still standing in not very splendid isolation opposite Millennium Point.

It too, though, is an exceptional example of Victorian architecture, also designed by Sir Philip Hardwick as a kind of echo of his Euston Arch, rather than a direct copy. Its overall height, and that of its columns, are almost identical, but the columns themselves are differently configured and in the more decorative Ionic style.

At the top of a short flight of stone steps is a formidable doorway, surmounted by the coat of arms of the London and Birmingham Railway, and alongside it a plaque commemorating 'the 150th anniversary of the arrival of the first London to Birmingham train at this station on Monday 17th September 1838'.

It was in fact a truer 'Gateway to Birmingham' than the more famous Euston Arch. It has, moreover, survived to be reputedly the world's oldest railway terminus still in its original location.

For a start, Curzon Street was quite simply the wrong place -maybe not for railway engineers, but certainly for passengers wishing to get to the town centre. With Victoria herself having only recently discovered Albert, there was no Albert Street, allowing horse cab drivers to take even more circuitous routes than they might have done anyway and charge a shilling (about £3.25 today) for the privilege.

Inconvenience notwithstanding, rail travel increased rapidly and by the 1850s four separate companies were operating out of Curzon Street, but it led almost inevitably to the opening in 1854 of the much more central New Street station and to Curzon Street becoming for the remainder of its active life freight-only.

That life, however, was a long one, and by the time the station closed in 1966, the Euston Arch had already been demolished, one of the saddest and more needless casualties of the 'comprehensive redevelopment' movement that led to the disappearance of great swathes of London and of many of our other most historic cities.

A particular regrettable aspect of the Euston Arch story was that the battle to save it had already been fought and won once, back in the 1930s. It was obvious even then that the original station needed extending, and the owners - the London, Midland and Scottish Railway (LMS) - decreed that the Arch would have to go as part of the renovation.

The Victorian Society, the national charity responsible for the preservation of Victorian arts and architecture, had yet to be formed, so its equivalent, the Georgian Group, of which the young John Betjeman had been a founder member, extended its titular historic remit and managed to persuade the LMS that the Victorian arch could be dismantled and re-erected further along the Euston Road.

The Second World War put paid to those plans, and, by the time they re-emerged in the early 1960s, we had had nationalisation and electrification, and 'the bloody British Transport Commission', to quote Betjeman, was determined to completely shed the steam image of British Railways, of which the Arch was all too prominent a reminder. It had to go, and be seen to have gone, completely.

The earlier compromise could still have worked. As with the recent re-siting of Sir Christopher Wren's Temple Bar, the only surviving City of London gateway, in Paternoster Square alongside St Paul's Cathedral, there could surely have been found, say, an historically appropriate hilltop site overlooking the present London to Birmingham railway - had the political will existed. But it emphatically didn't.

The Macmillan Government was Conservative, but desperate not to be seen as conservationist and therefore outdated. It was accordingly deaf to all the passionate pleas of the Victorian Society, its most prominent founding members - Betjeman and Sir Nikolaus Pevsner - and even to the columns of The Daily Telegraph. Ministers were not required to consult, as they would be today, before signing off listed building applications involving demolitions, and the Arch was swept away with most of the rest of the station in 1962.

For interested readers, the best account of these events is probably that written by Bevis Hillier in the third and final volume of his Betjeman biography, and there is a charming mini-movie viewable on the London Destruction website (www.geocities.com/londondestruction/arch.html.

The battle was indubitably lost, but not the war. It certainly furthered Betjeman's own reputation as a respected public figure able to persuade people to see merit in, and even care about, the unfashionable and prosaic. But, more importantly, it provided a major stimulus to the development of today's wide-ranging heritage and conservation movement.

It helped, in short, to change the way we see things - things like Curzon Street Station. In 1966 Birmingham City Council, to its considerable credit, chose not to follow the British Transport Commission, but to step in and save the station and, for its trouble, has spent much of the subsequent 40 years trying to find an appropriate function for it.

It looked until recently to have found a superb one, as a permanent home and state-of-the-art concert hall for the Royal College of Organists. Unfortunately, that plan fell through and the build-ing's future is again uncertain. What surely remains constant, though, is the injunction penned by Sir Nikolaus Pevsner back in the 1960s: "As the Euston Arch was wantonly destroyed, the Curzon Street Goods Station must be preserved at all costs."