Make or break: A journey into the unknown stress-tests a relationship / Getty Images

The man who pays his way

Even as the rain doused the quayside at Limassol, and fierce clouds jostled over the Troodos Mountains, at 8am on Wednesday I was in fine spirits after a "Pharaohs and the Promised Land" cruise. Then I met Robert Durrant, a retired cleaning contractor from Norwich in the Lido Restaurant on Deck 5, and we swapped stories about the trip just ended.

Climbing to the towering castle at Alanya in Turkey; being welcomed by the Egyptians on Alexandria's elegant Corniche; and clambering through the ruins of Masada, high above the Israeli side of the Dead Sea. After a week like that, who wouldn't feel fitter and happier?

Especially, he added, at the price he paid. A week of sleeping, eating and drifting from one Mediterranean port to another, including flights from London, cost Mr and Mrs Durrant a last-minute £550 each. I didn't mind in the slightest that I had paid rather more, because unlike Mr Durrant I had enjoyed an extra month of anticipation of the trip – a most important component among the rewards of travel.

Yet Mr Durrant's parting comment temporarily dented my good humour. I had booked the lowest-grade accommodation on board: a windowless inside cabin close to the engine room. So had Mr Durrant. But he had been given an upgrade, and had spent the week living it up in cabin 862, complete with porthole and, presumably, dazzling sunshine. As with Titanic, some passengers are more equal than others.

A touch of cabin envy aside, I certainly felt happier and healthier at the end of the trip. (I chose not to regard the unlimited food on offer as a challenge.) But a vague feeling of well-being is one thing; scientific evidence of the impact of a holiday is quite another. Which is why the pioneering research by Kuoni into the physiological and psychological impact of a holiday is to be welcomed.

The tour operator is offering free holidays to six people who are prepared be prodded, poked and psychoanalysed to measure the power of good that a holiday is supposed to do for you.

The happy half-dozen will be despatched to locations in Africa, Asia and the Indian Ocean. Researchers will measure stress and anxiety pre-departure and post-arrival, and the participants will keep "mood diaries".

Given that the experiment is being paid for by a holiday company, you might imagine that the results are a foregone conclusion: it is unlikely to demonstrate that we would all be happier and healthier if we stayed at home and closed the curtains, rather seeking out enlightenment, adventure or pure indulgence. But such is the stress involved in an overseas holiday, maybe not.

In normal life, you do not awaken at 3am and make your bleary, weary way to an airport in order to stand in a series of queues where you must demonstrate, repeatedly, that (a) you are who you say you are, and (b) you intend neither to circumvent hand-baggage regulations nor to commit mass murder. Between you and your final destination stand inclement weather and striking air-traffic controllers. In the event you reach your destination and decompress yourself from the cheap seats, you may well find that the locals have the temerity to speak languages other than English and to eat all manner of strange food. Throw in intemperate climates, dangerous creatures and unwholesome plumbing, and it's a wonder we don't all return as emotional wrecks. Happily for the travel industry, nothing seems to dull our appetite for venturing abroad.

I went off to fetch a cup of coffee for Mr Durrant, and reflected on three universal truths of travel. First, there is no correlation between pounds-paid-per-hour and the value of the experiences and encounters you acquire; next, memories of journeys boost long-term well-being; finally, the other man's cabin is always brighter.

For more on the Holiday Health Experiment see

Encounters of the backpacking kind

The fastest way to stress-test a new relationship and assess its long-term health prospects? Travel together. While absence may indeed make the heart grow fonder, close proximity on a journey is the best way to judge compatibility. Lazing on the beach or exploring ruins? Local cuisine or "safe" fast food? You quickly find what makes the other person tick, and sick.

This applies particularly on a make-it-up-as-you-go-along backpacking trip. Personal habits, foibles and preferences are all sharply exposed on the road. You can judge how well, or badly, the two of you respond to the unexpected joys and unforeseen calamities of travel.

After a couple of weeks of heat and dust, dodgy hostels and overcrowded buses, you should be able to tell whether a prospective new flame should become a permanent travelling companion, or despatched to the dating departure lounge.