When will I ever learn?

I hate shopping with my mother. Hate it. It all stems back to a time when I was young, had just started to drive, and she kept me waiting for THREE hours as she 'popped' into the shops.
'Twenty minutes max', she said.
It's a wonder to behold. She goes into a daydream and loses all sense of time and sense. So, I surprised myself when she asked me to take her to Booths our local supermarket so that she could buy 'a couple of things', and I agreed.
I went to Harrogate to pick her up and drove back to Ripon. She doesn't get out much so as she was coming for lunch I thought that it shouldn't be too bad especially if I timed it so that we had to 'be quick' because Jan was cooking and expected us.
The knot tightened in my stomach as we approached the store and in order to try and get some kind of control of proceedings I asked her what she wanted.
'Three things', she said, 'no four'.
Could this be true?
'I want some nuts, streaky bacon, cheese and water,' she said.
My original plan to go and drink some coffee, whilst she shopped, went out of the window. This might not actually take much time I thought. So I stayed with her knowing how easily she gets distracted. Whilst she propped herself on the back of the trolley I gently (but forcibly) guided it round the store.
I estimate that the cost for the 'four things' that she wanted came to around £16.
In fact we were in there for about an hour and the final bill came to £154.
Will I ever learn?