We have a keen sense of right and wrong in our family.

It is a simple concept: Wrong is what other people do.

As a pioneer of this attitude, I suppose I shouldn’t be surprised that it has caught on so quickly with the boys.

The other day Alec, aged five, raced into the room, his face contorted into a familiar combination of extreme injustice and tell-tale glee. “Harry and Kit have stolen the Christmas sweets,” he said, his voice wobbling.

“Now there aren’t any for me to steal.”

And with that a wail filled the room.

Harry and Kit of course knew nothing about the raid, despite brown mouths and a stash of wrappers under a sofa cushion.

To master the art of never being wrong you need a few techniques. One is to insist that this is absolutely the first time you realised a rule was being broken. (The “Really? He needs his own ticket?” approach). This is most effective when followed up by an immediate deflection of blame onto the accuser. (The “Well, why isn’t there a sign about it?” rejoinder).

When I caught the boys attempting to slide down the stairs on a massive Ikea cardboard box they used this technique to perfection.

“Why?” asked Harry. “We were only having fun.”

I reminded them of one of the few rules we try to enforce: No playing on the stairs for fear of injury, disfiguration and, most importantly, wallpaper damage.

“You never said we couldn’t surf on the stairs,” he replied, accurately.

It is an approach Harry, aged eight, uses quite often. Having spent 10 minutes lying in the shower cubicle making indelible hand prints on the glass, I quizzed him over whether any washing had taken place.

“Yes,” he said, unconvincingly.

“With soap?” I asked.

“Aww, you didn’t tell me to use soap!” he said.

I am currently drafting a pre-shower contract with a terms and conditions tick box to save us all a repetitive lecture every bedtime.

It also helps if you have a scant to non-existent grasp of how to behave in certain, if not all, social situations.

As I sat reading with Kit one day, he was suddenly sick all over me, himself and the sofa. While I shouted to my husband to come and help, Alec and Harry appeared at the door.

Before I could ask them to go and get some towels, Harry said brightly, “Do you want to do the Conga Kit?” Not deterred by his silence, Harry and Alec did an energetic conga round the room and disappeared.

When I pointed out that it might have been nice to ask if Kit was alright before partying around him, Harry stared at his vomit-encrusted brother.

“How was I supposed to know he was ill?” he said.

The worst thing that can happen to those of us in the always right club is to be falsely accused of wrongdoing.

“Mummy!” Kit wailed recently, clutching his head. “Alec hit me and kicked me and pulled my hair.”

Alec looked indignant. “I didn’t kick you!” he said.

Luckily more than one person can be right at the same time, which helps enormously.

Yesterday another raid on the Christmas sweet mountain was reported. My heart sank.

“Mummy, where’s my chocolate reindeer? I was saving it,” asked Alec.

“Oh”, I said vaguely, “Was that yours?” And gestured towards the kitchen windowsill, reindeer’s last known resting place.

“No,” he said firmly. “It’s gone.”

There was an awkward pause.

“Did you eat it Mummy?”

He was right, of course. I did.

Well how was I supposed to know he still wanted it?