I parked about 30 feet behind them (to give them plenty of room to reverse out), and waited, and waited, and waited and watched, and God I waited........................

The very elderly chap kept pushing the valve on the hose into the valve on each tyre, but he just kept shaking his head and shouting to the lady that it wasn't working, then he came over to me (I'd been sat waiting for at least 20 minutes by now), he said "I hope you're not waiting to check your tyre pressures because that machine doesn't work" - so I went to have a look.
I went over and Mrs elderly person was in charge of putting money into the machine, her hands were shaking violently (certainly not from the cold) and she couldn't tell one coin from another even with her specs on.
I said to her that it only worked with 10p, 20p and 50p coins (as that what it says in large writing on the front of the machine), and that 20p gives 2 minutes. She was handing coins to her husband(?) and asking "is that a 5p, 10p or 20p" (at least one of them was a 50p amongst 2p and 1p coins), he couldn't tell which coin was which either and his hands also shook. So I took over at this point to get them on their way as there were now 4 very bored drivers waiting in the queue. She had been filling it with 5 pence coins which it doesn't accept and they come straight back out.
I asked him what pressure should be in his tyres and that's when the fun really started, he said 24 psi at the back and 22 at the front - is that right for a rather large BMW estate as it seems rather low, does anyone know?
He spent ages trying to get the dust-cap off one of his rear wheels, eventually connected the hose and the machine said 30 psi, I said "that sounds about right for that car", but he was determined to reduce it to 24 psi. I said to him "so why not set the machine to 24 psi?" He didn't know that he could adjust the default pressure on the machine from 26 to another pressure by using the 'plus' and 'minus' buttons, the instructions are very clear and easy to read on the machine, so why can neither of them read them?
I think he suddenly felt suitably embarrassed at this point, he thanked me for my help and called it a day.
I got back in my car and waited for him to reverse back - eventually he moved about 10 feet (because he didn't use his mirrors and probably couldn't turn his neck), he did a 'several' point turn and drove off.