'Did you bring your own bags?' she said.
Stupid question. Why would I ask for bags if I had some already?
'No. I forgot.' Of course I forgot. I had spent the day ferrying children around, sorting out the house, and shopping was an afterthought.
'We're encouraging people to use their own bags.'
Yes I know that. I have a supply of the reusable ones at home. I just forgot. In the list of great crimes, where does that feature? Obviously quite high on the list.
'Could I have some bags please?'
A sigh. Not a quiet sigh, but one audible even to the people at the end of the queue. Be ready people. I noticed a man at the back discretely slide his trolley to an alternate queue. I wished I could join him.
Two pieces of orange plastic were thrown in my general direction, and the shopping started to move along the belt. The quantity of the latter did not seem to correlate to the former. And in her haste to dismiss my meek request the handle of one of the bags had remained in the stack of orange under her seat, meaning that I was now expected to fit several days supply of food into one small orange bag. Which was rapidly filled by two boxes of cereal.
'Could I have a few more bags?' A simple request. Said politely, no hint of sarcasm or suppressed rage.
'We're trying to encourage people to use their own bags'. Yes, of this I am aware. But its a bit late now. I am here, my bags are at home. Ergo, I need some of theirs.
'It's to help the planet. You know, stop global warming.'
I held her gaze and stopped packing shopping. Though the packing stopped because I no longer had anything to pack into. She saw the pile of produce at my end growing larger, and realised that I wasn't going to load it all into my trolley and go away shamefaced. She needed to dish the plastic once more.
Usually they pass you bags singly. Sometimes they even open them slightly to make it easier to start getting your purchases inside the bags and out of the shop.
A pile of orange plastic was flung to the end of the checkout. The bags were not opened. They weren't even separated. They were still firmly attached to each other, in the same condition in which they had left the orange plastic bag factory.
I had my revenge. I took each bag off the pile as I needed it. I packed slowly and carefully. And I didn't hand my card over until the packing was complete and everything in my trolley.
'Which is worse,' I asked, as I entered my pin number, 'to use your carrier bags instead of my own, or to drive all the way home and back again because I remember my bags are still in the kitchen?'
Her jaw dropped slightly. Her eyes flicked from me to the others in the queue. A smile flashed across someone's face, just for an instant.
'We're just trying to do our bit. Every little helps.'
'Wrong shop.' She really should learn her jingles better.
But the question hung there. No one answered. So which is worse for the planet? And in the grand scheme of things, how important are six plastic bags? And do they completely wipe out the good I did three times in the past two weeks when I have walked there instead of driving? Is my poor memory the sole cause of global warming? Have I brought about the downfall of civilisation because I am too busy to remember to stuff my car with thick plastic bags and instead rely on the thin plastic bags in the shop? And are bags that last for ten visits to the shop before disintegrating really any better for the environment than thin plastic bags that get reused for holding muddy football boots, transporting small amounts of goods between home and office, or visiting the butchers? Both are plastic, are both bad?
And if shops are rationing bags to do their bit for the environment, why do they use so much packaging on their products? Why are carrots in a plastic bag? Why are garlic baguette slices on a plastic tray inside a plastic bag?
'Well at least we're trying.'
It was over. I had lost. I had to admit my guilt and leave. I had forgotten my plastic bags, and the world will pay a terrible price. As I left, hailstones began to fall. It was all my fault. The world will end, and Mr Sainsbury will carry no shame, he has done his part. It is I that failed, it is I that wasted the planet's resources, and now the weather is exacting its revenge.