Feeling unhealthily cheerful this morning, I'm breezily chucking people's shopping across the till at a merry pace while making mindless smalltalk about the weather, the government, the best way to make raspberry jelly, and everything that's gone wrong with the country since we lost the colonies. (Can you tell the clientele are mostly pensioners?) For once, I'm even doing what we're supposed to do, and smiling. Oh the strain.

It seems nothing can dampen my spirits, until Mr World-Owes-Me arrives. He is a particularly nasty specimen of customer - the type who considers any contradiction an infringement of his human rights, and will raise hell over the pettiest thing. He's also not particularly polite.

"Hello", I greet him cheerfully. He ignores me. I scan his shopping through and announce the total. He vaguely chucks a card onto the counter in my vague direction with an unintelligible grunt, and mutters something about how the queues are too long and he had to wait all of a minute for the previous customer to pay and pack her bags.

I didn't need an excuse to be unimpressed with him, and now I'm just slightly peeved. I "accidentally" pass his card over the security tag remover, which just so happens to contain a strong magnet. Strangely enough, his card won't swipe. I make a show of vigorously swiping it fifteen or so times, before laboriously keying it in by hand.

"Looks like you'll need a new card - this one won't swipe" I tell him.

"Nothing wrong with it!" he snaps back. "It's almost brand new."

"Well it's not working." I announce so that the whole queue can hear. "Are you sure it's valid?"

By this point, his face has turned an interesting shade of crimson. I ponder whether to stop there, but hey, where'd the fun be in that? I hit Clear and the transaction pauses. I make some clucking noises and ring for the supervisor. As she approaches I call out very loudly "I've got a card here that's not being authorised!" At this point, his knuckles are protruding by an inch as he cringes at the back of the till. Of course, once we key it in again, it all works perfectly. I put on a hugely false smile and a very patronising voice.

"I'm SO sorry about the problems. Maybe you should ask your bank for a new card?" With a fuming grunt, he snatches his reciept and makes a sharpish exit, setting off the door alarm thanks to the soft tag I attached to the the sleeve of his jacket. I know our security guard is very entheusiastic, so I hope he'll enjoy a stripsearch.

A few customers later, I get one of the regular mathematically-challenged. She's been to the sale area and grabbed a few half-price bargains, but seems to have difficulty working out what that makes the £1 items she's picked up. I'm only too happy to tell her that half of £1 is £2. And the fiver extra that appears on the bill goes a long way to keeping me in chocolate for the day.

At lunchtime, I go to visit a friend in a shop further down the mall. Despite having completely different uniforms, I'm often mistaken for an employee/tour guide by the customers.

"Where are your shampoos?" asks one. I gesture so vaguely I could be indicating half of the shop (which is pretty accurate) and mumble "mmbbmm aisle mmmm next to the mmmm." Not wanting to sound helpless, the hapless customer wanders off into the ether, as I step away from the entrance to the shampoo aisle behind me. He'll find it eventually, after wandering through the sanitary towels and wart removal creams. The scenic route, some might call it.

I get to the bakers for my usual pasty, just for some obnoxiously loud woman with two brattish kids to step in front of me and take the last steak pasty. I resist the urge to knee the tots headfirst into the sandwich cabinet, take a chicken pasty with remarkable restraint, and seethe quietly. I'm not beaten yet.

Returning from lunch, who should be coming through my till, but the aforementioned frump. Her bratty kids have had their sticky fingers all over the Pick'n'Mix and are guzzling bottles of pop that haven't yet been paid for. Some people have no patience. I get the sweets girl to re-weigh the sweets, adding a few pound coins onto the scales for "extra value", then put them in a bag underneath a leaky bottle of bleach. Well, at least they'll be clean.

The rest of the afternoon zooms by, and I'm ready to go home. I cash up my till, using the time honoured "one £20 note for you, one £20 note for me" method of counting, then make a hasty dash for the back door. Unfortunately, some tedious old fart who's too blind to see I'm carrying a till and in a hurry accosts me on the way. He wants a lightbulb to match a screwfit one he's brought with him, so I find him a bayonet-capped one and tell him he may have to force it in. With the power turned on - it helps it secure the connection, I tell him. I even give him the trick of the trade - to improve energy efficiency, he should insert his thumb into the bulbholder to clean the contacts while switching the power on and off rapidly. I'm just too kind at times.