My four grown-up children are political, passionate about justice and the state of the planet. So I wasn’t surprised when Megan announced she was vegan. Lily and I were already vegetarian; it didn’t seem a big deal to factor in another dietary requirement. There was also a part of me that wondered if the veganism was a phase.

I underestimated my daughter. Not only did she remain vegan, but her siblings were swiftly converted, too. Ed and I lagged behind. But after Megan made us watch Cowspiracy and Earthlings, reaching for dairy would never again be a simple act. We had the information and couldn’t un-know it.

We are now, in effect, a vegan household. I have given up my daily dose of bio-yoghurt. Ed has even given up his beloved strong cheddar. But toast and honey is my go-to comfort food, and has been for as long as I can remember. I can’t sacrifice honey – there is no debate on that – but, as a goodwill gesture, I have switched from cow’s to goat’s butter, although I am probably kidding myself that goat’s butter is acquired in a kinder manner.

My offspring cannot forgive this weakness. Particularly the butter. When they berate me for eating it, I am in turns angry, defiant and depressed. I feel hounded in my own home, and when I’m cornered, I resort to lashing out. After one particularly heated argument, Ed and I escape to the pub to recover. Ed orders scampi fries. I eat one and feel like a rebellious teenager. I know my feelings do not make sense.

“Where did I go wrong?” I wonder bitterly. “Why do they think they can bully me? They ate meat all their lives until about five minutes ago, and now I’m not allowed a tiny bit of butter.”

I’m aware that I sound like a petulant child. But it feels good to moan. Ed nods. “We pay the food bills, we enable them to be vegan, and yet we end up looking like the bad guys.”

“Exactly. It’s easy for them to be perfect,” I say. “They don’t have to worry about council tax and mending the washing machine. They’re still protected in their bubble at home.”

“Yes,” says Ed sadly. “But they do have the moral high ground. I think that’s what’s so difficult to accept.”

He is right. I’m angry about being made to feel guilty. And that is a very uncomfortable place to be.

I try vegan margarine, but it is not for me. I have a solution. It is not grown-up or noble, rather born of desperation (and greed). I pretend to give up butter, but hide it in plain sight in a honey jar. The vegan children never touch honey. So they won’t know that I’m actually spreading butter on to my toast.

This works for some weeks. Peace reigns. I almost forget there is a problem. As far as the children are concerned, I’m eating the disgusting margarine. What could go wrong?

A friend of Jake’s stays the night. In the morning, while I’m out walking the dogs, he requests honey on his breakfast toast.

Returning from my dog walk, I am met with a frosty silence.

“What’s the matter?” I ask, a little nervously.

Then it starts. A barrage of anger, disappointment and righteousness. The friend is curled up on his chair in mortification. Of course, I go off on one, as they would say. I bring up all the points that Ed and I discussed and throw them in their faces. I tell them they can’t accuse me of not being an animal-lover when I keep three dogs and two cats, when I’m 99% vegan. “I am not a bad person,” I wail. “Leave me alone.”

We do not speak for several days. And then we do. There is forgiveness. They agree that as I’m old and stuck in my ways, it might take me longer to be a purist.

“But what we can’t forgive,” they say sternly, “is that you lied to us.”

Anger bubbles up again. I have to swallow it. They are right. I lied. But being scolded like a child by your children is not something I relish.

Unlike butter.

Names have been changed.

• Saskia Sarginson is the author of The Stranger (Piatkus, £7.99).