My mother devised The Sandwich Rule. The Sandwich Rule said that all school lunchboxes must contain two savory sandwiches and two sweet. There should also be an apple, a container of yogurt, and a packet of crisps (potato chips) on Tuesdays and Fridays.
When Mum made our sandwiches, my sister Sarah and I opened our boxes in the canteen of Bowl Alley Lane Junior School in Horncastle to find two cheese and cress sandwiches and two more filled with raspberry jam. Or two ham and tomato sandwiches and two neat brown bread triangles spread with honey, to be eaten in that order.
But when Dad packed our lunches, the boundaries were blurred.
Dad took sandwich duty very seriously. He tried to concoct the kind of sandwiches he would have been pleased to find in his lunchbox when he was a schoolboy.
A good sandwich as far as Dad is concerned is built of thick rounds of bread. Doorsteps, they're called in Leicestershire, where he grew up.
Dainty tea party sandwiches filled with translucent discs of finest English cucumber are not part of Dad's culinary repertoire. He also believes that good sandwiches contain lashings of peanut butter.
His favorite fillings are peanut butter and cheese, peanut butter and raisins, and peanut butter and jam. That can make classification a little difficult.
Peanut butter and blackberry jam is fairly obvious. Those sandwiches are sweet.
What about peanut butter and cottage cheese with pineapple? I guess those are savory.
But if you open your lunchbox to find you've got two peanut butter and beef spread sandwiches and two rounds of ham and mustard, you've got a big decision at your fingertips: Which do you eat first? Dad said it was up to us to figure it out. "Peanut butter is good stuff," he insisted.
My mother sighed and said Dad would eat peanut butter for breakfast, lunch, and supper if she didn't stop him. She still let him make our sandwiches, though.
When I left England, I gave up peanut butter. At least I thought I had.
Paris was a feast of other things: pink and green marzipan confections from northern Africa sold in the exotic 17th arrondissement, crumbly leek tarts eaten during leisurely Saturday lunches, and sugared chestnut puree you could mix with crème fraîche.
I guess I could have found a jar of peanut butter if I'd been really desperate.
The Galeries Lafayette - a plush department store in the center of Paris - had a special English shelf where there were tins of bright orange baked beans and bottles of spicy Worcester sauce waiting for expats craving a taste of home. There must have been the odd jar of pâte d'arachide lurking somewhere nearby.
I never looked for it. Peanut butter was part of my past, and I was moving on.
But then I came to Zimbabwe, where peanut butter suddenly reappeared on my menu.
There are rows and rows of jars of oily peanut butter for sale here, despite shortages of other goods.
This peanut butter is thinner and browner than the stuff Dad brought us up on.
Peanut butter is far from just a sandwich spread in southern Africa. It's an essential ingredient in several dishes. Like dovi, one of the local specialities I've learned to love.
You make dovi by simmering a few pieces of chicken for an hour with a sliced onion, water, two chopped tomatoes, and four fat tablespoons of peanut butter.
As I ladle out the sizzling stew in the pitch-black evenings of Africa, I think of Dad laboring over two small nut-scented lunchboxes all those years ago.
You were right, Dad. It is good stuff.