I had always wanted to explore Bulgaria. It had been one of the most remote of the countries behind the old Iron Curtain, though today the British seem to be busy buying property there. I had long been interested in its modern history, what with the "Bulgarian massacres" of the 1870s provoking Gladstone's campaign that the Turks should get "bag and baggage" out of Europe, so hastening the end of the decaying Ottoman empire. And I was intrigued that the first monarchs, Ferdinand and Boris, both liked driving trains in their new kingdom. In fact, I had travelled through Bulgaria before, back in 1974, on a sleeper to Istanbul, but all I saw of it then was the cheerful delinquents who came into our compartment with a suitcase full of women's shoes that they were smuggling into (or was it out of?) the country.
This time, I entered Bulgaria on a train from Romania. I was with a film crew making a series of television films about a journey from London to Istanbul, called Orient Express, after the famous train. Coming from Bucharest, we crossed the Danube to reach Ruse, where, in 1883, the passengers on the inaugural Orient Express had to take a local train to Varna on the Black Sea and thence a boat to Constantinople. We, however, continued south. I had hoped we could travel on by train, especially as - on the map - the railway across the mountains ascends in a series of exciting loops. Alas, both time and the budget required that we continued by road. So we boarded a people carrier and set off for Plovdiv.
Our first Bulgarian "fixer", painfully smart in dark glasses, did not inspire confidence. Main roads seemed to be the deadly three-lane highways we had in Britain in the 1950s, and he kept cheerfully overtaking at high speed on blind corners while conducting conversations on his mobile phone. The only thing to do was shut one's eyes and hope, pray . . . Once, I opened them to find that we were going the wrong way down one of Bulgaria's few dual carriageways. We survived. But when, as light fell, we began to ascend the Balkans - the mountain chain that gives its name to the entire peninsula - by roaring around hairpin bends at high speed, the director's nerve finally broke and he asked our fixer to slow down so that we might live. This, however, was the best bit of the journey, because we had to go through the dramatic Shipka Pass where, in the 1877 liberation war, a small number of Bulgarians and Russians successfully repelled a sizeable Ottoman army.
Then it was down into darkness and into Upper Thrace - once called eastern Roumelia - through which countless invading armies have moved over the millennia, in and out of Europe. There were still hours to go, not helped by the fact that, in the absence of any visible road signs, our driver got lost and had to ask the way. Dinner was a horrible takeaway snack purchased at a garage shop.
Eventually we arrived at Plovdiv after midnight, and found that our hotel was a modern building standing in the usual dreary communist wasteland of 1960s concrete slab blocks, of which every town we had driven through seemed to consist. Could this really be a city that can boast of being older than Constantinople, Rome and Athens, the coeval of Mycenae and Troy?
Things looked better in the morning, but I found myself alone at breakfast. It emerged that the director and the cameraman and the soundman had all been violently ill in the night. That garage stop had been a mistake. No filming could be done, so I had the morning and Plovdiv to myself. And once I had crossed the River Maritsa into the old town, I found that it really is a city of great antiquity and interest. It was at one time called Philippopolis, after being conquered in 342BC by Philip II of Macedonia, while the Romans called it Trimontium, the city of three hills. These hills are impressive, more like miniature mountains.
The city centre is also rewarding, with more Roman remains and two 15th-century mosques - reminders of this region's long and largely placid Ottoman history - among many Orthodox churches and some good examples of Bulgarian art nouveau. Again as is typical of the old eastern bloc, Plovdiv is full of monuments. One of the most significant, if not the best, was erected by the Jewish population to commemorate the sadly unusual fact that the people of Plovdiv resisted the German demand to round them up.
Back at the hotel, I found the film crew still incapacitated, so Ognian, our next and much better fixer, whisked me off into the country for lunch. As we sat by a waterfall and consumed fresh trout and the local Mavrud red wine, he talked of Bulgaria's complex and, in the 20th century, unfortunate history: how the last communist government had forced the large Turkish minority to take Slav names and forced many to leave; how the daughter of Todor Zhivkov, the last communist dictator, a cultured woman who was keen on celebrating the anniversary of the medieval Bulgarian kingdom, had died in "mysterious circumstances" - probably at the hands of the Russians; how this polluted, forcibly industrialised peasant country was coping with the challenge of joining the European Union. Then he took me to see the medieval monastery at Bachkovo, celebrated for its remarkable icons, on the old Roman road through the mountains to the Aegean coast to the south.
By the evening, the film crew was recovering. Pale and frail, they managed to film me standing on the wide deserted platforms at Plovdiv station, waiting for the (very late) sleeper from Sofia that would take us on to Istanbul. I had hoped that insurance money would enable us to come back to Bulgaria to do justice to Plovdiv and to this extraordinarily interesting, complex and still little-known country, but it was not to be. Clearly I must return by myself, by train of course, and see the capital, Sofia, as well. If only there could be a new Orient Express to take me all the way in the non-polluting comfort that railways - in the post-cheap-flight era that must surely come - can provide.
"Gavin Stamp's Orient Express" is on Channel 5 on Tuesdays, 7.15pm