It's a momentary lapse of judgment, but it's enough to suggest my brain isn't functioning at optimum capacity.
Five bottles of Heineken into the Herald's drink-driving limit trial, I've mistakenly veered towards the ladies' toilets. I also consider having a cigarette, which is odd. I haven't smoked for more than six years. Despite the descending fog the signs are pretty clear. I'm mildly intoxicated.
Five Heinekens (6.5 standard drinks) is one beer beyond my personal no-drive limit, but the breath alcohol tester we've borrowed from the Drug Detection Agency shows that at 220 micrograms per litre of breath (mcg), I'm still below the proposed new legal limit of 250mcg, and well under the current limit of 400mcg.
Downing a sixth Heineken, within two hours and 13 minutes, pushes my reading up to 290mcg. My notes record that I'm "a bit pissed". I'm at the point where driving would be irresponsible and, soon, illegal. Under the new law this kind of breach would attract a fine and demerit points.
My colleague and drinking buddy, photographer Sarah Ivey, isn't faring quite so well at the six-drink mark. She's just finished a bottle of wine that runs to 7.8 standard drinks.
"I feel like I'd crash walking down the stairs," she says.
Despite her obvious intoxication, Sarah blows 390 - just under the current limit.
After two 125ml glasses of wine Sarah was already feeling it. She is an average-sized female of 58kg, and her 220mcg reading at that point was under the new limit, but she wouldn't have been comfortable driving.
After her third wine, she blows 350. "I'm half chopped," she admits. At this point I'm at 230mcg, closing in on the new limit.
Food changes things. With our fourth drinks we eat a bowl of hot chips and some spare ribs. The effect is startling. My reading drops from 230mcg to 200mcg, and Sarah - who was expecting to be well over 400mcg - dips to 310mcg.
The fifth drink is where I go wandering into the ladies. I'm clearly slightly impaired, but my reading has increased only to 220mcg. Sarah is back up to 340mcg, still well below where she was pre-eating despite having two more drinks on board.
There have been concerns that motorists who have a glass of wine or two with a meal might find themselves criminalised under the proposed law changes.
The Herald's experiment suggests that is unlikely, even allowing for a significant variance in the way humans metabolise alcohol. Light drinkers would seem to have little to fear under the current law.
Sarah's convinced her sixth drink will be her last. She blows 390mcg.
I conduct an American cop show-style sobriety test. I can touch my nose and walk in a straight line no problems at all.
Sarah's hit the wall. Her pinot gris tastes like poison and she can't go on. Finally she blows 410mcg. "That's f****** ridiculous," she says.
It is. After eight beers I'm approaching the current limit. I'm at 390mcg. One more should do it. It doesn't. No change. Must have been the garlic bread.
I'm in danger of missing the ferry home and we've almost blown our $150 budget. I chop Sarah's left over wine and throw down a double rum. Five minutes later I blow 430mcg. My notes say I'm now too pissed to do something that might start with a w and have an m and u in it.
It's been half an hour since Sarah's last drink so she should have metabolised most of the alcohol in her system. Her reading climbs to 430mcg.
Half an hour later I retest myself on the ferry. I've misplaced my note pad, and giggle about how I'll almost certainly forget where I'm recording the reading. It's at 9.40am the next day that, through the fog of a decent-sized hangover, I find 420 scribbled on a box of batteries for my dictaphone.
An hour after I finish drinking I'm back to 390mcg, legally able to get behind the wheel of a car. Instead I crack open a bottle of red wine. I'm already three sheets to the breeze anyway, so what the hell. Before bed I take my final reading. 390mcg. I'm well hammered, but still okay to drive.
All up, I drank nine 5 per cent beers, half a glass of white wine, a double rum and half a bottle of red wine over eight hours.
After six beers I was over the proposed new driving limit, but I only briefly topped the current limit.
I never went near a car, so the stagger into the ladies' was about as dangerous as it got. Worse things happen at sea. And on the roads. It's hard not to wonder how that momentary lapse of reason would have played out if I'd been driving instead of walking.
I wouldn't have copped a drink-driving charge, but that could have been the least of my worries.