My sister makes jam. She makes it with a devotedness that involves experimentation and the regular tweaking of recipes, adjustments that she records in a notebook for the next time. She cannot bypass her Syrian green grocery without slowing her pace to see what he has on offer. Blueberries for conserve, tomatoes for chutney, a plump heel of ginger to candy so that we can suck on it between cups of tea, its syrupy bite nipping the inside of our mouths.

She stuffs plastic bags into jacket pockets when she goes walking, just in case: in case she stumbles upon windfalls or bushes bowed with blackberries which bruise her fingers blue as she plucks them greedily, occasionally stabbing her skin so that a bud of blood swells. She has collected the necessary accoutrements of a serious jam maker: a proper preserving pan, the right sort of thermometer. She nags friends to keep their empty jars. She rescues her own from the recycling bin. Her kitchen is often heady with the treacly scent of boiling sugar, surfaces streaked strawberry pink and sticky.

I ask her, ‘Why jam? What do you Love about it? Where did you find this passion? When?

‘I love it all’, she says, ‘the whole process: the finding the Fruit, the deciding what to make, the trying out new recipes, the testing and tasting’. When I stay with her, I bear witness to this, these sampling sessions, piles of warm toast at breakfast as we try the latest batch and she fastidiously takes cognisance of comments and criticism: ‘this is too sweet …. this too runny’ and then – of a Lime, Lemon and Ginger Marmalade – ‘this is perfect’, exactly the right balance between tart and sweet, the consistency obediently spreadable.

‘I love being able to gift friends something homemade.’

She tells me she began to experiment with jam making when she ten or 11, ‘when we lived in Sotik’, a lonely tea farm in Western Kenya. The garden was forested with fruit trees – loquats bowed branches so that you could pick amber berries and suck their flesh clean off shiny stones, and mulberries stained bare soles black. Its warm fecundity, though, in a place where sunshine and regular rain conspired to make everything grow thick and fast – especially the tea where new growth was plucked regularly and tossed into the back borne panniers of the pickers – was in stark contrast to mum’s mostly barren internal landscape; our new geography’s isolation stripped it back to bleak nothingness; she spent long months unwell. One year six months at a stretch, no respite.

‘I did it because I didn’t know what else to do, because there was all this fruit … because I had to do something.’

She knew. She knew then, even so young, the imperatives of Keeping Busy.

My sister is a scientist. A chemistry teacher: she interprets the mysteries of matter and reactions and the Periodic Table to teenagers.

But by the time she was one, long before she stood in a lab conjuring magic in test tubes for her students, she had mastered the alchemy of happiness.

She is one of the happiest people I know.