I’m always jotting ideas; this year in this lovely notebook, a present from the BBC. Let’s see. For Sunday lunch I was at my daughter Annabel’s and what she’d done is cut a butternut squash in half, removed the seeds, put olive oil on top and roasted it in the oven. I thought “This is brilliant”, because I’d long been fannying around cutting butternut squash into reams, or cutting myself while potato-peeling it. Now I’ve got this bee in my bonnet and want to tell people “Roast it whole until the skin’s soft, take it out of the Aga, cool it a bit and it will be just lovely”.

Whenever my husband serves me tea or coffee he asks “Sugar?”, knowing full well that for the 50 years we’ve known each other I’ve answered “No thank you”. That’s because during the war my mother said: “If you give up sugar in tea and coffee, I’ll be able to make the odd cake, stale bread and margarine pudding, or rhubarb and crumble.”

I have an older and a younger brother and as children we’d get up, have breakfast – toast and marmalade – and then go out and make all our own entertainment. We had secret dens in the woodland and built our own garden shed with warm running water – we’d pour water through a kinked pipe above a fire and into a bowl. Nobody interrupted and said, “An open fire against a shed wall is highly dangerous.” We fried eggs and cooked beans in tins, wrapped flour and water around sticks to heat and melted Fox’s Glacier Mints on spoons. I seem to remember that, being a girl, it was me doing most of the running around arranging things.

When I was paralysed by polio at 13 I went into an isolation hospital and couldn’t sit up, so I only took liquid food from spouted cups which the masked nurses would bring in and feed to me. I saw my parents only through glass; we couldn’t touch. I recovered but it left my left arm and hand weak and whenever I’ve been on TV, viewers have contacted me, saying: “Forgive me for writing but I couldn’t help noticing you suffer arthritis and I’d like to suggest a remedy.” It’s terribly nice but its poliomyelitis.

My parents went to the head teacher at Bath Grammar when I was 16 and said “What could Mary do?” and she replied “I don’t know, very little. Perhaps she could be a child’s nurse” and my father said “I’d pity the child”. But I was in the first bunch of pupils who could choose between Latin and maths and domestic science for school Cert and there was a brand new domestic science department opened, in a lovely mews. My teacher there was Miss Date. Knee high to a grasshopper she was the most wonderful little woman who made cooking fun and told me I was good at it. I’d never baked with mother but when I brought home a treacle pudding, father said it was as good as mother made.

At 17 I went away to Pau in the south of France for a few months to study domestic science – including cleaning windows with newspaper and water – while living with a Catholic family with 10 children. I’d left my pony at home and on the journey I kept seeing horses’ heads in villages, then the first night the family served me horse meat and I cried and I cried. Tears poured down throughout the meal but they took little notice. I just hated it I wasn’t allowed in their kitchen during the day and didn’t go in there at night because there were rats.

While studying institutional management I did work experience preparing canapés in a big long shed at Heathrow where I was novelty value, being the only British person working there. For the Monarch flights, foie gras was cut into sausage shapes, decorated, put in the freezer, then I’d pour hot aspic over them. I remember every canapé to this day.

Dad thought something very fishy was going on when, at 22, I was offered a job for £1,000 a year – more than Dad paid his own staff – for inventing cheese recipes and writing leaflets at the Dutch Dairy Bureau in London. Four of us girls took a flat at 31 Thurloe Street, with a fridge, a Baby Belling and a cabinet with a pull-down surface. It was squalid but we thought it was great. I remember coming out of South Kensington station one evening and seeing these very strange new things on sale (at the greengrocers) called avocado pears. We’d each put £1 a week into the kitty for suppers and often entertained boys from a flat in Sydney Place with our avocados. Those boys are coming to my 80th birthday party this month. But of us four girls since, Pippa died of cancer, Gilly was killed in a plane crash (on the way to my chalet in Switzerland) and Penny – the brightest of us all, the head girl at Rodean – has Alzheimer’s. So haven’t I got a reason to go on doing what I do? Why wouldn’t I?

The only time I’ll use a microwave is to warm up a cup of coffee I’ve left too long before drinking.

You could take my best, finest cut-glass and drop it on the floor and it won’t bother me, because nothing compares to the death of a child. Losing our son William [in a car crash, aged 19] was a terrible, unbearable experience and we lost our joie de vivre and appetite for a very long time. We didn’t go out when invited and survived on homemade soups. Then I had a cook school and it all came back. Cooking and baking is both physical and mental therapy.

Mother, who lived to 105 and fed herself until her dying day, had started the Friends of the Royal United Hospital in Bath after noticing many patients weren’t visited and couldn’t get a cup of coffee. And I went back recently and now they have 400 volunteers who make homemade cakes and visit patients. It’s a legacy of my mother that I’m more proud of than anything I’ve ever done.

I got chubby as a teen and then when my children were young, I was half at home and half at work and there were all their crusts available at home and all my cooking and testing at work and it all went on my bottom, as it may. But I’ve had my bottom under control for the last few years.

I’d drunk wine every day until I had a new knee in the new year. Each night since, my husband has said, “A glass of wine, Mary?” and I’ve said no. But I’m out with the girls tomorrow night and think I’d better get back to normal.

Mary Berry’s Absolute Favourites is out now (BBC Books, RRP £25). Click here to buy it from the Guardian Bookshop for £20