Their conversation over the next ten minutes touches on Leandro, who had jogged every morning on Ipanema; on Vasily, also a keen runner with an obsession for football – ‘He is hoping next term to be school captain’; on Katya’s absent husband Gennady, a Ukrainian oil executive. As she begins to explain his job, Dyer realises that he has met Gennady already, at the headmaster’s annual Fathers’ Breakfast beside the Cherwell; Dyer had recognised him in a flash as one of those noticeably short men who pack out first class in long-haul flights, with a wide black moustache, large square teeth, and tinted glasses, although it was overcast.

As to Katya, Dyer formed the impression of a nice, evasive, professional wife, who was aware that she stood out because of her natural good looks.

The composition of the teams had long been settled by the time of their next encounter, after the February half-term. Katya bustled and smiled when she collided into Dyer on the Woodstock Road. It had rained for two days; now the sun was out. She was dressed well, expensively. Pearl-grey jacket, a bit early for spring, brown cashmere jersey. Her pleated blue skirt was the colour of the airmail envelopes that Dyer would post his father from Brazil.

Dyer was awkwardly relieved that she did not bring up the subject of football. Both of them heading in that direction, the Phoenix School was what she wanted to discuss. Dyer seemed to fascinate Katya when she discovered that he had been a pupil there.

She was light-hearted in her attitude towards him. ‘Excuse me, but why are all female teachers called Ma?’

The school’s customs and rules perplexed her. What was this thing Minus? What did it mean, ‘out of bounds’? And why, unvarnished nails on slender hips, did she have to make an emergency taxi-drive to Boswell’s to buy her son a diabolo!

Sex. The furnace which smelts mud into gold. With no effort, she made him giddy. He felt his hardness, and tried to diffuse it by very earnestly answering her questions.

Dyer knew what it was to be a foreigner. Prey to a potent blend of obligation and history, he untangled for Katya the expressions and traditions of which the ultra-spin diabolo was but the latest phenomenon – and already being superseded by gel pens that smelled of apples.

When she looked at his lips as he spoke, as if it would help her to follow, his groin tingled.

So they walked together down Canterbury Road, through Park Town towards the Phoenix School, with Dyer telling her in his most contraceptive voice about marbles, jacks, conkers (‘I like the way you say conkers’), Airfix kits, Action Men, stilts, superballs, Frisbees, fidget-spinners – all trends requiring stock, with pressure to purchase from shopkeepers who knew exactly how to supply Phoenix mothers like Katya with the appropriate currency.