Thank you for this simple, to the point, sensible advice.
Seems logical once you know.
Tube is punctured but not quite fully flat, knobbly tyres stopped wheel from dropping out, after coming onto forum ( not before consulting 3 books) and reading this post I went out and released the last bit of air then just squashed tyre in at sides and out came the wheel.
I had worked out where I would have to undo the brakes if it came to it but didn't want to.
My favourite brakes are cantilever, next are these side pull, worst are V brakes but I don't see cantilever these days. I've never had cantilever or side pull squeal like V brakes do matter what pads are used. Am glad I'm not forced into undoing the side pull.
Cheers