They are two of the remotest islands in the world, and two of the last remaining, and still loyal, outposts of the British Empire.

Martin Cowell climbs aboard the world's only working Royal Mail ship, along with consignments of everything the islands need from teabags to tractors for a South Atlantic adventure.

IT WAS not an auspicious start to the trip. All was darkness as our flight arrived in Cape Town, after a major power failure in the city and it was raining!

However, it doesn't take long for this stunning city to show its better face the massif of Table Mountain generates a series of micro-climates and by the time we actually reached the city from the airport the sun was already breaking through.

But after only three days of sightseeing and acclimatising, it was time to board the RMS St Helena.

The passenger cargo-liner, the only working Royal Mail ship in the world, can carry 128 passengers with 65 crew and officers, as well as up to 1,500 tonnes of cargo.

As well as everybody who wants to get to and from St Helena, everything needed, from tea-bags to tractors, travels on the ship.

The officers, a mix of Brits, South Africans and Saints', as the islanders are known, resplendent in their whites', welcomed us aboard.

There were also opportunities to visit the ship's bridge another feature of the informal atmosphere.

On our third morning out of Cape Town, we arrived at Walvis Bay, Namibia, with vast sand dunes rising behind the town.

We took a guided 4x4 drive, seeking out the unique wildlife of the Namib Desert and our guide, suddenly spotting a chameleon in a bush, was just amazing as he leapt out the car, captured it and then fed it beetles he'd picked up (David Attenborough would have struggled to better it).

Back on board, the three days to St Helena were a perfect introduction to the island, chatting to the friendly Saints. Copies of the online St Helena Herald, gave ample detail of local political fallings-out. And for those who are interested, the burning topic is the proposed airport: it will change island life for ever; and RMS Saint Helena, with her annual operating deficit of £1.5m, is due to cease service in 2010.

The days passed gently, with time to scan the (thankfully) calm ocean for the occasional flying fish.

At the Captain's cocktail party I met the Governor, who had just been on the ship's annual visit to Tristan da Cunha, for which he is also responsible, and a UK government economist, whose brother works for the Oxford University Press in Oxford.

Discovered more than 500 years ago by the Portuguese, St Helena has been in English hands since 1659.

Ascension Island is 703 miles, and the nearest African mainland is 1,200 miles away the expression the middle of nowhere' comes readily to mind.

The most prosperous period for the island was also its most famous; after Napoleon arrived in October 1815, the population rose to 8,000, twice as many as now.

British citizenship has recently been restored; now Saints, especially the young, are leaving in droves.

We anchored off Jamestown, the capital, at first light. The arrival of the island's lifeline is an obvious cause for excitement and noticeably more Saints than visitors lined the rails as the sun rose.

Officials came out on tenders including British-uniformed police with a sniffer dog to detect drugs and then we transferred ashore.

The capital spreads up the steep valley looking like a small English country town, with attractive Victorian buildings lining the main street.

We were taken past the castle seat of the island government police station, courthouse, and prison, up to the quaint Consulate Hotel, with its wrought-iron balconies.

A walking tour gave us the history, and some insights into island life. What quickly becomes clear is the absolute dependency, economic and political, on UK government support, with 70 per cent of islanders employed by officialdom (the island lacks the resources and infrastructure to be self-sufficient, and one concludes that most locals prefer it to stay that way...).

The island tour in a dilapidated 1929 Chevrolet charabanc took us to the Briars, where Napoleon spent his first two months, then on to Longwood House where he lived and died, and finally to the tranquil site of his burial.

His remains were long ago removed to Paris, of course, but the French government has purchased all these sites to ensure they are preserved.

St Helena packs great scenery into its 47 square miles a cross between the Hebrides and the Scillies, perched on a vast and remote volcano.

We drove down steep narrow lanes through Half Tree Hollow to stunning views over Sandy Bay, then to Rosemary Plain, where we had lunch at Farm Lodge, a hotel created by two former RMS St Helena officers.

All too soon we had to leave this paradise.

Again, there were hundreds at the wharf.

Now the majority of passengers leaving the island were Saints. For many, it would be months or even years before they returned.

As the ship prepared to weigh anchor, a huge (but harmless) whale shark swam lazily around; then we departed for Ascension a major source of job opportunities for islanders.

The atmosphere was much like the bus to work. Though there was still time for bingo and cricket.

At the deck barbecue, I talked to several Saints, including the housekeeper to a top racehorse trainer at Newmarket. Previous travellers were keen to regale us on Ascension's limited appeal and the no frills' RAF flights, actually operated by a charter company as the service's planes are either involved in the war on terror', or just plain broken beyond repair...

Ascension, the peak of a vast dormant volcano, was discovered by the Portuguese in the same year, 1501, as St Helena and the Royal Navy occupied it in 1815 to stop the French using it as a base from which to rescue Napoleon.

Once described as hell with the fire put out', its 35 square miles and lunar landscape have a value out of all proportion to its size it was of critical importance as a stopping-off point during the Falklands war although the United States Air Force has run the base since 1956. The stark landscape bristles with signals antennae, both civil and military.

Getting ashore for the last time on this trip involved some nimble leaping from ship to tender, with a further change mid-stream, before we reached the dock.

Georgetown has few buildings of great age but the vehicles are on a different scale from those on St Helena all that RAF and USAF money, no doubt.

The Obsidian Hotel was the Government guest house until private ownership was allowed only a couple of years ago.

With no public transport nor taxis, a hire-car was needed to get around the island astonishingly green at the highest point, after work by experts from Kew Gardens in London.

Alongside frigate birds, there were feral donkeys, especially on the golf course (with not a blade of grass). The highlight had to be nesting green turtles, which had made the long journey from the waters off Brazil.

Led by conservationists, we went at night to beaches close to town, then returned at first light to see the last females return to the sea.

And so to the airhead' for the flight back to Brize Norton.

Meanwhile RMS shuttled back to St Helena, and thence via Tenerife home to Portland in Dorset it would be another two weeks before it arrived.

* To book just the holiday, go to www.vjv.co.uk * To book just the cruise, go to www.rms-st-helena.com