Occasionally my wife objects to some of the things she says in this column. It is not in my nature to apologise for being merely accurate, and I usually just point out that she had no such objections when she said those things in real life. On reflection, however, it seems politic to make a renewed effort to blur the line between fact and fiction, to protect the privacy of those concerned. This precaution will not, I hope, undermine the basic truth of what follows.

So anyway, my partner – we’ll call him Sean – and I are driving to the country to stay with friends for Easter, along with our two adopted ex-research chimps, Anton and Kurt. Our friends have three adopted chimps of their own, and many leading primatologists would question the wisdom of putting so many apes under one roof for three nights. Indeed, that is what I am doing as we crawl along the M3.

“What about two nights?” I say. “I have a landmark study to finish.”

“You can finish it there,” says Sean, who doesn’t respect my work.

Kurt makes the sign for “Are we there yet?”, but I pretend not to see.

We arrive just before dark. For the five chimps, the first order of business is to establish a strict linear dominance hierarchy by shooting each other with foam darts fired from several shoulder-borne weapons. Their alarm barks echo throughout the small house as darts fly past my head.

After an hour of shooting, the chimps switch to some karaoke game, which quickly becomes competitive. They take turns to emit an endless cycle of screeches at top volume, in a bid to mimic Adele’s Rolling In The Deep. I wonder if I should include something about this in my landmark study, but I’m worried other primatologists might question my methodology.

On Easter Sunday, the chimps spend the morning painting eggs, until they are all a uniform sludgy brown. Afterwards, it is traditional for our friends to roll their eggs down a nearby hill, but we’ve never done this and Anton is mystified: he makes the sign for “What’s the point?” (a shrug, followed by a finger raised in the air).

Our friend looks at him, and then looks at me.

“It’s just not something they would do in the wild,” I explain.

The sun has shone all morning, but as the hour of rolling approaches, the weather turns alarming. The sky grows dark; rain falls sideways. The painted eggs are still wet when we load everyone into cars. I make the sign for “What’s the point?” to Anton in the rearview mirror, and he shakes his head so hard that his ears flap.

“Stop it,” Sean says.

We pull in at the base of a tall, steep ridge. As we climb to the top in a gale force wind, I suffer a sudden resurgence of the vertigo that has plagued me for a fortnight. I fall behind.

The first few eggs come flying at me like grenades: forcibly peeled of their shells as they bounce, exploding into hard-boiled mush either side of me. By the time I reach the top, most of the eggs have been rolled, and it is clear from Anton’s distinctive pant-hoot that he now sees the point.

Going downhill is even more difficult. At first I make an attempt to keep up with everyone, but after a while I stop and wait for Sean to reach the bottom, so he’ll have a better view of my struggle. When I next look up – about halfway – Sean is already in the car.

I take a few careful steps, concentrating on my feet. Sean starts beeping the horn.