Who scoffs noodles on the go? Live wire Alfie, 20, rushing down a Japanese city street with his best mate Owen at the outset of the new fourth series of the travel challenge show Race Across the World (BBC1), was shovelling the stringy dinner into his face.

This, the boys were told, breaks a taboo in Japan, where walking and eating is considered shameful. For older generations at least, it's largely unacceptable in Britain, too — not that Generation Z knows or cares.

Munching chips on the seafront might be all right, but slurping noodles on the pavement is pretty disgusting, wherever you do it.

Foreign food was presenting all sorts of difficulties to the five pairs of travellers. Betty, 25, was trying to persuade her younger brother James — four years her junior and three times her size — to sample oysters.

Each couple gets £27 a day plus a money belt to keep it safe, a GPS tracker so the film crews know where they are, and a map of the world

Each couple gets £27 a day plus a money belt to keep it safe, a GPS tracker so the film crews know where they are, and a map of the world

Their challenge is to get from the north of Japan to Lombok in Indonesia, travelling 10,000 miles overland and by sea, for no more than the cost of the air fare: £1,390

Their challenge is to get from the north of Japan to Lombok in Indonesia, travelling 10,000 miles overland and by sea, for no more than the cost of the air fare: £1,390

'It smells,' he protested. James isn't the adventurous type. 'My idea of travel,' he said, 'is getting drunk with the boys. You know, Magaluf, Ayia Napa...'

The Majorcans are going to miss him awfully this year.

At least Stephen and Viv, described as 'a retired husband and wife', can be relied on not to get legless on shots of sake or walk down the road with their faces in fodder bags like cart horses. Both in their 60s, he's had a heart attack, she's had a stroke. Let's hope their travel insurance doesn't come out of their total budget, or they'll be sleeping on park benches.

Each couple gets £27 a day plus a money belt to keep it safe, a GPS tracker so the film crews know where they are, and a map of the world — or, as the narrator John Hannah says it, 'a wurrruld map'.

Teacher Eugenie, 61, (left) had the next best thing to an app ¿ her 25-year-old daughter Isabel (right), who cornered people on public transport and cajoled them to teach her the language

Teacher Eugenie, 61, (left) had the next best thing to an app — her 25-year-old daughter Isabel (right), who cornered people on public transport and cajoled them to teach her the language

Their challenge is to get from the north of Japan to Lombok in Indonesia, travelling 10,000 miles overland and by sea, for no more than the cost of the air fare: £1,390. They began by handing over their mobile phones, with lots of nervous bowing, to a priest smiling enigmatically outside a temple in Hokkaido.

Last year's series of Race Across The World was set in Canada, where distance rather than language was the problem. This time, a translation app would be invaluable, since most Japanese don't speak English. Teacher Eugenie, 61, had the next best thing to an app — her 25-year-old daughter Isabel, who cornered people on public transport and cajoled them to teach her the language. Even a limited vocabulary proved a huge advantage. The duo arrived at the first checkpoint before their rivals.

So far, we're getting to know the racers and no one has been eliminated. The sightseeing is perfunctory, and it's difficult to believe they're able to pick up extra cash by doing odd jobs such as washing rickshaws or picking wasabi. But it's great fun guessing who is in the lead and who has taken a wrong turn, as they chase a £20,000 first prize. My money's on Alfie and Owen, if they aren't felled by noodle indigestion.