A FEW summers ago some fairly elderly friends came to swim, and a little poolside chat revealed that Moïse, 68 and counting, was afraid of losing his memory. He had an awful problem, he said, with the simplest things, his children's names, wh

A FEW summers ago some fairly elderly friends came to swim, and a little poolside chat revealed that Moïse, 68 and counting, was afraid of losing his memory. He had an awful problem, he said, with the simplest things, his children's names, why he'd gone into his garage, where the salt was kept. The answers came to him eventually, after enormous effort. He put this weakness down to mental disorganisation, so he said he was going to train his mind with regular exercise and iron discipline.

First, he was going to learn by heart the numbers of the French départements. The départements, as I don't expect you need me to tell you, are the administrative divisions of France, like counties in the UK or the USA. They date from the Napoleonic aftermath of the French Revolution, when the old provinces (Touraine, Béarn, Languedoc, Berri and so on) were abandoned in favour of smaller, more easily administered units, in which the golden rule was that it had to be possible to ride from the centre to any point in one day.

Mostly the new units were named after geographical features, like the Dordogne from the river that flows through it, or like the Jura from the mountains that cover much of it. But not all: one, indeed – but why don't you look at the competition at the end to see where this leads us? Much later they were given numbers, and the most obvious manifestation of this is on vehicle number plates, where the last two figures refer to the département the car is registered in. More recently they've been used as the basis of post-codes, where the first two numbers of the five-figure post-code denote the département, and if ever you want your mail to be delayed you have only to miss it out on the envelope.

So this is what Moïse set himself to do, to learn all the département numbers, from 01 (Ain) to 95 (Val d'Oise), a task slightly eased by their being roughly in alphabetical order. But that wasn't all for Moïse. Learning what the French call les numéros mineralogiques wasn't anything like stringent enough: next on the agenda were the French area telephone codes. Un défi, a challenge, to be sure. But he was determined to show his memory who was boss.

Months later I asked Moïse how he was getting on. Not well, he said: he'd maybe over-reached himself after all. 01 – Ain; 02 – Aisne; 03 – Allier, he told me, but he stuck at 04. He knew them, but he just couldn't call them to mind. A film of sadness passed over his eyes: he would have hoped that someone called Moïse (the French for Moses) would have been able to get up to 10 at least.

MAYBE SOMETHING Moïse could have tried is an in-car game which might reduce levels of boredom in the back as you speed through France in search of the sun next summer.

The rules are simple. Allow yourself any French vehicle in any situation, moving, parked, clamped, in a used car lot, scrap heap, anywhere except in a picture or on a television screen. (You may be tempted to these expedients as the game becomes desperate or even suicidal.) The trigger is seeing a vehicle with 01 as the last two numbers on its registration plate, meaning that it comes from the Ain département, north-east of Lyon and bordering Switzerland. You're off: nothing will content you until you've seen 02, then 03, then, whizzing past poor old Moïse, 04 (Alpes de Haute Provence), 05 (Hautes Alpes) and 06 (Alpes Maritimes, so the vehicle probably comes from Nice). By this time you're hooked, calling down curses on the heads of the palsied inhabitants of the Ardèche (07) who never allow you so much as a distant glimpse of their wretched wheels and threatening with blue murder not only the entire population of the Ardennes (08) for lying so invisibly low but also the driver of the car who says casually 09? Ariège? Why, I saw one only 10 minutes ago when we stopped for petrol. Don't tell me you missed it! Because, of course, you have to see it with your own eyes: no proxies allowed.

And if your passengers start suing each other for criminal assault, malfeasance and perjury don't come grumbling to me about it. I only mentioned relief of boredom.

A FEW years ago, about the time Moïse was struggling to stave off what you've already diagnosed as Alzheimer's, the Tarn département (81) put forward a plan to re-organise the local gendarmerie. Among the proposals was the closure of the gendarmerie at Mousse le Grieux and the transfer of its staff several kilometres down the valley. As always when anyone tries to tamper with the status quo there was outcry in Mousse les Grieux, demonstrations, petitions and all the usual paraphernalia of public outrage, and as a result the village was allowed to keep its gendarmerie, a fine 19th-century mini-château with handsome wrought iron gates.

Some time later Madame Bot, an elderly lady who lived in the first-floor flat opposite the Crédit Agricole, was disturbed in the early hours by the sounds of crowbar on hinge and high-speed drill on cash dispenser. She peeped across the road and saw several hooded villains breaking into the bank. Living in the flat alone, she tiptoed to the telephone and summoned the immediate aid of Mousse's noble police brigade. She drew up a chair to the window to watch the unfolding drama.

Minutes passed, five, ten, fifteen. No police, although the gendarmerie is all of two minutes' walk from the Crédit Agricole. After 20 minutes the swag-laden villains roared off in the direction of the neighbouring Hérault département (34). 'You fools,' Madame Bot shrieked down the telephone, 'You've let them get away! You could have caught them red-handed! And that's my money they've stolen! Why didn't you come at once?'

'We can't get out, Madame,' an exasperated gendarme replied. 'The robbers chained and padlocked the gendarmerie gates on their way to the bank . . . '

COMPETITION

OK, heads down. 2 Questions, and you've got to answer both to qualify for the prize:

1. One French département appears to be named after a knock-out spirit distilled from apples. What is its name and what is its numéro mineralogique?

2. A few sentences above there is a hidden parody of part of a cautionary tale written by an Anglo-French poet and author who was born in 1870 at La Celle de St Cloud in the Yvelines département (78). What was his name, and what was the title of the cautionary tale?

First correct e-mail answer wins a signed copy of my book 'French Leaves: Letters from the Languedoc'. Bonne chance – and bonne année too, while I'm at it.