THE upholstery was on the firm side, and it wasn't the smoothest of rides, but as the mustard-yellow train clattered through tunnels and over gorges I knew it would be the most comfortable seat I would get in the next few days.

My journey on the Taieri Gorge Railway had started from the magnificent Edwardian station in Dunedin on New Zealand's South Island, once the gateway to the city for passengers and freight travelling to and from far-flung farming communities.

But my passive enjoyment of the scenery ended after just 60km (40 miles) at Middlemarch. The rest of the Otago Central Railway that ran in an arc cross-country to Cromwell was closed in 1990. I was heading for the Central Otago Rail Trail - a well-maintained 150km trail that offers up to a week's traffic-free cycling.

So while most of my fellow passengers took a stroll before boarding the train back to town, I joined the cluster round the guard's van to catch bags and bicycles as they were handed down.

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After a comfortable night in the Royal Hotel, the pub in the country town of Naseby, I clamped my compulsory helmet on my head and set off.

I have tramped some of New Zealand's greatest trails, through the lowland rainforest of the Hollyford Track, up the rocky paths of the Routeburn Track, and across pristine yellow beaches on the Abel Tasman Coast Track, but have never explored the country by bicycle. As I put feet to pedals, I hoped the scenery would not spin by too fast.

Starting from the picturesque green goods shed at Wedderburn, subject of an “iconic” painting by Grahame Sydney (New Zealand's answer to Edward Hopper), I encountered the only slight steepness in my two-day ride to Alexandra, a town founded in the 1860s gold rush. A bit of a pant was rewarded with a rest stop at the stone monument marking the 45th parallel. I was eating an apple at the midway point between the South Pole and the Equator. It is distractions like this that are so welcome on a long ride with only uninterested sheep in fields on either side for company.

More great excuses to dismount are the gangers' sheds dotted along the trail. Reproductions of the huts used by the men who maintained the tracks, they house maps and interesting info-boards on the view and local history. And at each station I passed I stamped my “passport”, available locally for $10 (about £3.70), with proceeds to the rail trail trust.

Another timely break came at Hayes Engineering Works, right by the trail at Oturehua, filled with early 20th-century agricultural tools and machinery, but alas, no café.

While accommodation of various sorts, from camping upwards, is offered at one-day intervals, lunch and snack spots are in short supply. Ravenous at 2.30pm, I wobbled up to the converted school bus café at Lauder, renowned for its coffee, to find only a few processed cheese sandwiches. The owner-managers of Kokonga Lodge, a boutique B&B right on the trail, have just started serving elevenses, light lunches and teas to passing cyclists.

The most spectacular riding was through Ida Valley, with its bone-shaking viaducts of tightly packed sleepers, and Poolburn Gorge, where I had to dismount and find my way through two tunnels using a torch. Emerging blinking into the sunlight, I scanned the gorge in vain for the rare native New Zealand hawks that live there, but saw other swooping birds.

After clocking up a respectable 50km, I stayed at Tiger Hill Lodge, a modern B&B with tip-top en suite bathrooms, where you can self-cater if you wish. It is a minute from the trail at Omakau, and a short walk to the pub, where I had a slap-up fish dinner with wine from the region.

At the end of the summer season there were few other cyclists. On my second day I passed some hikers, and felt glad to be bowling along, because for all the trail's charm, the long straight stretches with nothing but sheep and turnip fields would be rather monotonous at walking pace.

After another 25km, as I gingerly lifted my aching bum off the saddle for the last time, I looked proudly at the nine stamps in my passport. I had called at only half the stations on the trail, but felt as if I had passed my Cycling Proficiency Test all over again.

NEED TO KNOW

Discover the World (0870 0603288, www.discovernewzealand.co.uk) offers 14 nights' self-drive from £2,120pp, with B&B, car hire, ferry crossings and Cathay Pacific (www.cathaypacific.com/uk) flights to Auckland. A four-night add-on Central Otago Rail Trail package, including bike hire, transfers, B&B and Taieri Gorge Railway, is from £435pp.

Information www.newzealand.com

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