Right! What am I offered for these two chicken legs? Corn-fed chicken legs, lady, and just reached their sell-by date.

What's that? You'll pay £1.50 for them? Don't be silly.

Tomorrow they'll be whiffy and not even fit to feed the cat so we'll let you have them at a bargain price. How about 75 pence? Yes? Done!

And yes, had I not checked my supermarket bill very thoroughly I would indeed have been done. I would, in fact, have paid £7.55 for two ageing pieces of chicken flesh, which works out at about £35 for an entire bird.

If I had just one piece of advice to offer the world it would be this: always check your supermarket bills.

I do as a matter of course nowadays, which is how I came to discover that I'd been charged £7.55 for two chicken legs in a supermarket belonging to ...

Well, as it was obviously a genuine mistake (I hope!) it would be churlish of me to name the company wouldn't it?

Oh, go on then, I'll give you a clue. Let's just say the company name began with an S and it was neither Safeway or Somerfield.

Not that Safeway or Somerfield - or Tesco, Asda, Waitrose and the Co-op come to that - should feel complacent. I reckon that over time I've probably lost a couple of hundred pounds (sterling, not weight) thanks to errors at their checkouts.

Alluring 'special offers' stacked on the shelves lose their appeal when you discover you've been charged full whack for them in your basket.

And 'Buy One Get One Free' makes a mockery of your budget when you buy one and pay for three, while a 66p bag of Jersey Royals leaves a nasty taste when you realise you've been blagged for £1.66 a bag at the checkout.

Top of my cheating checkout stories concerns the friend of a friend. Shopping without his wife to offer guidance, he filled his trolley.

Included in his shopping were three loaves of bread and when he got home he checked his bill and discovered he'd been charged £30 for the loaves.

Name the supermarket chain ...? No. It happened some years ago so that wouldn't be fair. All I'll say is that it wasn't one whose name began with an S - or a W or a T for that matter.

So, are we alert and looking at our bills? What's that? Three pounds of plums, a partridge AND a pear tree?

"Have you ever noticed that the mistakes that occur at checkouts never work to the customer's advantage?" I asked a friend the other day.

"I've never been knowingly undercharged in all the years I've been shopping in supermarkets."

My friend smiled slyly. "Oh, it's not unheard of," she replied.

"Just this week I discovered I'd paid for only one jar of coffee but I had two in my basket at the checkout."

I was stunned. "Did you go back and offer to pay for the other jar?" I asked.

"Well I only found out what had happened when I got home," she said as if this explained why she hadn't.

"Come on, which supermarket was it?" I inquired. "Does its name begin with an S or a T? Or could it be a W or possibly an A ...?"