My two grandsons are staying with us here in Provence for a week. Roman soldier Catriona flew from Marseille to Stansted and back in a day to get them out. Oscar, aged 11, is a regular summer visitor and knows the ropes. Klynton, ten, is here for the first time.

Klynton is what used to be described as ‘a bit slow’. At school he stays two years in the same class to everyone else’s one. He is a cheerful, polite lad with a phenomenal memory for football statistics. He can hardly dress himself but can tell you that last season Sadio Mané scored 11 goals with seven assists and is 29 years old and 175cm tall. Also, he tells me, he hasn’t seen his grandad for two years and one month.

Normally Klynton leads an orderly life centred on a shared bedroom in a very small house in Basingstoke in which there is no hugging. Led by a weary Catriona, the two brothers came crunching up the path at midnight dressed head to toe in Primark. Klynton’s T- shirt said ‘Global’; Oscar’s said ‘Future’. Our first cuddle for more than two years in the warm darkness was a clumsy one.

Today is the third day of their week-long visit, which has coincided exactly with a heatwave. During the day Klynton bears the 40ºC of heat stoically under a broken Panama hat with a paisley-pattern headband.

Factors here other than the heat which are most surprising to Klynton are that people speak a different language; that Grandad is bald and plays blues harmonica into an amped microphone with his eyes closed, moving his body ecstatically; that otherwise Grandad prefers to lie down if possible; that apparently all of Grandad’s friends live in enormous villas with private swimming pools set in botanical gardens; and that the ants are so big.

Our days begin with a round of cuddling. Klynton accepts his woodenly while looking away. He chews his morning croissant, still warm from the artisanal baker’s oven, as though it is the nastiest thing he has ever eaten. ‘How is your croissant, Klynton?’ I say. ‘Bollocks,’ he says. He and his brother are licensed to use this word descriptively while they are in France, as part of a household linguistic free-for-all in which English is liberally sown with comically pronounced French words, with west of Scotland colloquialisms, and with Basingstoke school slang.

After breakfast, given the viciousness of the rocketing sun, the only plausible outdoor activity is to find a swimming pool and sit in it. The first day we spent in four swimming pools. The first pool was kidney-shaped, deep in the middle, shallowing towards the edges. Klynton and Oscar are thin as lathes and paper white. Neither swims. What they like to do is take a running jump and make a big splash, clamber out and repeat till the cows come home. Near the first pool was a sort of Bedouin tent with flimsy curtains tied back. Already exhausted by his undemanding early morning exertions, Grandad lay inside groaning with fatigue and the heat like a Sultan expiring on his divan.

After an hour we walked a hundred yards down a shady lane and through two gates to where there is another pool which we have been invited to use whenever we like. This one was a large oblong, set in a lavender garden. Klynton, who had never before in his life suspected the existence of, let alone seen, let alone taken a running jump into a privately owned swimming pool, thought this pool was better than the first one because it was bigger.

The afternoon was spent in the foreign correspondent’s infinity pool set high up on a remote hillside. He is currently planning an electric fence to prevent wolves coming on to his property and eating Mary, his spaniel. Floating on one’s back in this pool on a hot day is like dying and going to Heaven. Klynton thought this swimming pool slightly less good than the second because it wasn’t as big.

In the evening we went to party with stewarded car parking and professional catering at a house with an enormous swimming pool with gigantic inflatable flamingos to ride on and underwater coloured lighting. By now Klynton was bright red and had rubbed the skin off the underneath of eight of his toes and six fingers. And he was now as tired as his Grandad had been all along. As he berthed his flamingo to accept a sausage roll from a passing silver tray, I said: ‘And so how do you rate this pool?’ He just looked at me stupefied, as if I or he or the world had gone mad and he wasn’t sure which it was.