I was doing a mega-shop at Sainsbury’s. It was my turn to cook for our Sunday food group. The moussaka recipe called for one kilogram of lamb mince. As fortune would have it, I could buy 2x500g boxes of mince for £4, saving me 30 p!

I like budgeting, so receipts hold a special fascination. As I left the checkout I mused over it, trying to calculate how much I was spending to feed four people in grand style.

Then I saw:

Lamb mince        Â£2.15
Lamb mince        Â£2.15

Jibbed! I couldn’t believe my eyes. Unlike the shops back home in Melbourne, Sainsbury’s has never let me down before. Despite the constantly changing landscape of discounts, they’ve never gotten the price wrong… until now.

‘It’s only 30 p, Joan,’ I said to myself. ‘Let it go.’

I slowly started walking to the exit.

‘It’s a mistake. They should know that there’s something wrong with their system,’ my other self argued. ‘Someone else might kick up a big fuss. You can save them the trouble.’

‘It’s 30 p!’ I protested. ‘Who else would complain? I’ll look like a loser.’

‘It’s Sainsbury’s job to deal with these things,’ the other self replied. ‘And you can buy a chocolate bar for 30 p.’

Before I knew it, I had done an about-turn and was headed to the customer service podium.

‘Hi. Would you mind checking the lamb price?’ I said, handing over my receipt. ‘I think there was a special on it.’

The two assistants didn’t bat an eyelid. ‘Of course,’ said the female. ‘Peter, could you go down and check the lamb? Ma’am, do you have the item with you?’

Another Sainsbury’s employee heard this as she walked by and stopped. ‘The lamb? It should be £4 for two. Saving of 30 p.’

‘So it’s not recognising the code,’ Peter said, examining the box of mince I had handed over. ‘I’ll have to fix that.’

They highlighted the mistake on my receipt, took a 20 p and 10 p coin out of the cash register and gave them to me.

‘Sorry about that,’ they said.

‘That’s okay,’ I said. I was just happy that they hadn’t made me feel like a skint.