Just after I purchased my A, I had to clean out the carb. So I pulled it down cleaned out all the rust flakes and dirt, which was blocking all except the main jet. At the same time, the venturi was badly corroded swollen and cracked, so I turned a new one up in the lathe. After putting it all back together, fired up the old girl. Adjusted the carb, running sweet. The next day, go on a club observation run, fill her up at the start. Fifty miles later, needed to fill up again, what?....oh no. Yep, forgot to screw the GAV seat back in. Got home, and there it was, sitting on the workbench waiting patiently to get put back into service.
I've also done the 'forgot to turn the fuel tap on' and also 'turn the ignition on' thing at various times in all my vintage cars.
There's only two type of people who don't make mistakes, those who don't work and liars.