I have decided that going further afield will lessen the chances of my being spotted and harassed by constituents, and save me the bother of having to wear my balaclava. Now I wish I hadn't bothered.
"We'll pick Josh up from work, and then go and do a quick shop," says Max, which sounds like a reasonable plan at the time.
The trouble starts when Josh doesn't finish work when he's supposed to and then, when he does finally get into the car, he claims that he's too tired to traipse round Morrisons.
By now, I can't face it either. I just want to get home quickly in time to watch The Killing, though I'm not expecting to want to kill my son by the time it starts. Or not yet, I'm not.
"I suppose I'll have to go in by myself, then," says Max. "While you two lazy buggers stay in the car and lounge about."
Which is fine by me, or was - until Josh suddenly opens the car door and gets out.
"Where are you going?"I say.
"Ssh," he says, then rushes over to the Photo Booth machine situated outside the shop. I watch as he fumbles around in the slot where the photos come out, before he comes running back to the car, yanks the door open and throws himself headlong onto the back seat.
"Got it," he says.
Before I can ask what he's got, I see a man pull back the curtain of the booth and step out. He goes to the slot and removes what is presumably a strip of photos, looks down at them, and then jerks his head up and starts scanning the car park. He doesn't look very happy at all.
"Who is that man, and what's he doing, Josh?" I say.
"Shut up, Mum, and tell me when he's gone." Josh seems to be fumbling about and trying to put something into his wallet.
"What have you got there?" I say, at the same time as I make a grab for it. Call it maternal instinct, but I just know when Josh is up to something.
I turn on the interior light, to find myself looking at a photograph of the man that I can see out of the car window. A single photograph, with one neatly torn edge.
"Josh," I say. "What is this? Why have you got a photo of that man over there?"
"He's the Photo Booth repair man," says Josh. "He gives me and the lads hours of fun."
"How?" I say - though I really should know bloody better.
Josh explains that he and his friends are regulars in the Morrisons car park. Which sounds very dodgy indeed, and doesn't get any better when it becomes apparent that their target is the poor repair man.
"He comes once or twice a month," says Josh. "And he gets into the Photo Booth, starts fiddling around with the machinery and then takes some photos of himself. Then he carries on working inside the booth for a while - with the curtain still drawn across the front. When he's finished, he picks up his photos to check whether they've come out okay."
"And your involvement in this is - ?" I say, though I'm not at all sure I really want to know.
"Well, as soon as the photos come out, one of us rushes over, and grabs them out of the machine," says Josh.
"What - you steal his photos?" I say.
"Not all of them," says Josh. "We just tear one off the strip and then put the others back into the slot. Confuses the hell out of him."
"Hand it over," I say. "Now, or you're grounded."
Josh glares at me as he passes something over the back seat.
"Joshua," I say, in disbelief. "There are twelve different photos here. How long has this been going on?"
"About six months," says Josh. "He's getting crosser every time it happens."
I can no longer deny the fact that I am, quite clearly, the parent of a juvenile delinquent.
*See here for another reason why Josh should never, ever be allowed into car parks without being accompanied by his parents.