In 1973, Jane and I bought Inter-Rail tickets and headed for the Greek islands. We were 18. Last year, we were 50. To celebrate, we decided to do it again.

We backpacked the first time, but now, it seemed, Jane had hurt her shoulder. She was apologetic as she told me she’d bought a suitcase with a trolley handle. But she also had some good news. She’d found our 1973 journal in her attic. Full of comments about how awful our heavy rucksacks had been. Secretly relieved, I returned my backpack to the shop.

Rereading the journal was hilarious and discomfiting in equal measure. There were endless names and descriptions of the people we’d met and the ones we’d “fancied”. But the highlight of our trip was clearly the island of Ios, where we’d slept on the beach. Jane and I agreed that we had to go back.

Before the era of low-cost flights, the cheapest way of getting to Greece was by train. A month’s Inter-Rail ticket cost just £33, and you had to be under 26 to buy one. Fortunately for us, there’s now no age limit, and youth hostels make no stipulation about “youth”. So we decided, in the spirit of ’73, that we’d stay in hostels where possible, although most of the ones we’d been to before had closed down.

We also decided that while our quest was to reach Ios, we wouldn’t stick to the same route as last time, through West Germany and Yugoslavia. (After all, they no longer exist.) When we arrived at Calais, I asked the woman at the information desk if she could suggest an itinerary to Austria. Her jaw dropped, but she started tapping at her computer.

“Whereabouts?” she asked. “Anywhere,” I replied. “Maybe Vienna?” Jane left the arrangements to me, as I speak French ... but obviously not that well: as we set off, clutching our printed timetable, we realised we’d been directed to Vienne in France, not Vienna. But we thought we might as well go there anyway.

Vienne, near Lyons, turned out to be wonderful. It had vibrant street cafes and a spectacular castle, and there happened to be a rock concert that night, so we had a musical accompaniment as we wandered about.

The next day, we set off again for Vienna. We got as far as Lausanne when a woman on the train said: “You can’t go through Switzerland without stopping at Montreux. You’d love it.” There was a youth hostel there, so we thought we’d try it out. It turned out to be right on the shores of Lake Geneva, and within minutes Jane and I were swimming in the lake, hardly believing our luck. It felt a bit strange sharing a dormitory with four young Swiss girls, wired up to iPods. But they were friendly enough.

In the morning, we started out for Vienna yet again. When we reached the station, however, we found there was a train about to leave for Milan. We jumped on, enjoying the random nature of our journey. We never did get to Vienna.

WE’D MADE a conscious decision to travel without guidebooks or train timetables, and to rely instead on personal recommendation and whim. When we arrived at stations, we’d gaze up at the departures board. If the train we had intended to take didn’t leave for hours, we simply caught another one that took our fancy.

So, in a haphazard fashion, we worked our way southeast. We took pot luck with the hostels. Some were fabulous: in Reggio Emilia, we were the only guests in an ancient monastery with enormous marble hallways. In 1973, some had been pretty unsavoury. At Zagreb, we’d noted in the journal that the youth hostel had been so smelly, we’d opted to sleep in a park. I wrote to my parents: “We’ve been sleeping in the park in Yugoslavia, but don’t worry. We’re with some Swedish blokes, so we’re quite safe.”

This time, we took the ferry from Italy to Greece — it was rather classy, with escalators and a swimming pool — and another from Piraeus to Ios, which certainly wasn’t. Hordes of us raced on board to stake our claim to the benches, and the deck was teeming with bodies and trolley suitcases. Hardly anyone was travelling with rucksacks, I noticed. I found it impossible to sleep. In any case, I was too excited. I’d moved so far out of my comfort zone, I was exhilarated.

Just after dawn, we arrived. Last time, we’d ignored the people holding signs saying “Rooms to let”. Now we were only too grateful for them, and struck lucky. Our hotel was exceptional, and cost us each only £14 a night.

As part of our teenage pilgrimage, we took a bus up through the village towards Mylopotas beach, the one we’d slept on. In 1973, there were no cars on Ios. The main transport was by donkey. Farmers would bring their sheep and goats onto “our” beach, and parts of it had been covered in droppings. But we’d loved sleeping under the stars and, according to the journal, had changed into our white cotton nighties every night before climbing into our sleeping bags. (We’d been to boarding school, and thought this was normal behaviour.)

Nowadays nobody is allowed to camp on the beach, and in any case it’s crowded with parasols, pedalos, shops and bars. We had a quick swim, then went for a beer. Back at the hotel, we’d caused quite a stir. “Are you the friends who were here in 1973?” they asked. “We’ve heard about you, but you don’t look old enough.” How we loved it.

Ios is now known as a party island, and we expected it to be completely spoilt. But in spite of signs entreating you to “Eat, Drink and Be Naughty”, or to drink 100 shots in 100 minutes, it’s still beautiful. It has more buildings, but they’re still in the traditional whitewashed cube style, draped with bougainvillea. If you walk past the port, you can leave behind the noise of cars and hear goats with bells round their necks. And the views are spectacular.

As we climbed up the old donkey track to the main village for supper, the streets were filling up. Everyone looked under 25, and we felt as if we’d gatecrashed a student party. But we couldn’t believe how friendly our fellow drinkers were, inviting us to nightclubs and pouring out their (short) life stories. One of the clichés about turning 50 is that you become invisible. But here, with so many young people around, we stood out.

Relying on personal recommendation, we found a tiny beach called Valmas, which became our favourite haunt. Perhaps because of a strong sea breeze, it was often deserted. And we were able to skinny-dip off the rocks — something we wouldn’t have dared do when we were 18. There was just one bar-restaurant, perched above the water, and we spent hours there, reading, writing and, in Jane’s case, sketching.

One evening we returned to the Ios Club, where, in 1973, we used to watch the sunset. They still played classical music. Last time, we’d sat on the rocks outside, as we couldn’t afford to buy drinks. This time we ordered Greek beer and sat on the terrace, feeling like millionaires.

A TEXT arrived from home. “Are you arriving back tmrw?” Guiltily, I remembered telling my husband I’d be away for just two weeks. Time to head for home. No rush, though.

We’d become railway enthusiasts, marvelling at the scenery. Some trains were crowded and dirty, but most were excellent. We jettisoned routine: it was liberating to eat when necessary, rather than at mealtimes, and I now knew that, just like my 18-year-old self, I could sleep in my clothes. At the start of our journey, I’d had trouble putting my suitcase in the luggage rack. Now I was swinging it recklessly over my head.

The last night of our trip was in Paris. We had dinner in a karaoke bar, and I still can’t believe Jane persuaded me to sing You’ve Got a Friend with her. Our singing was so below standard that our audience fell silent. One man put his head in his hands and said: “You should have warned me.” But instead of being thrown out, we were bought red wine, champagne and roses. By the early hours, we’d befriended enough people to join us for a group version of Help. We were 18 again, if only in the mind.

Retrace their steps

THE MODERN Inter-Rail network is a lot bigger than when Alison Waters stepped aboard in the 1970s. It now covers 30 European countries, as well as Turkey and Morocco. The principle is thesame, though: one ticket, thousands of trains.

THE TICKETS

Inter-Rail passes come in three versions. Anyone planning an extended trip like Alison and Jane’s should buy the month-long all-zone pass. It’s valid in every participating country and costs £405, or £285 if you’re under 26.

The two other tickets cover smaller areas and shorter times. A one-zone pass lasts for 16 days and costs £215 (under-26s £145); a two-zone pass lasts for 22 days and costs £295 (£205). For a zone map, visit www.interrailnet.com.

Note that sleepers and express services often cost extra; and a few privately owned lines don’t accept the passes. Ferries from Italy to Greece are included in some tickets, but ferries in Greece are not — book them at www.greekferries.gr.

UK companies selling Inter-Rail tickets include Rail Europe (0870 584 8848, www.raileurope.co.uk), RailChoice (0870 165 7300, www.railchoice.co.uk ) and International Rail (0870 084 1414, www.international-rail.com).

PLANNING

Alison chose to make it up as she went along, jumping on and off trains at whim. Some argue that’s the only way to Inter-Rail: it takes full advantage of the freedom the ticket gives you.

If you want a little more certainty, though, two books are essential. The Thomas Cook European Rail Timetable (£13.99) is authoritative and comprehensive; and the same company’s Europe by Rail (£12.99) has a wealth of brief city guides, with hostels, hotels and restaurants, for rail centres across Europe.