I was dismantling some mains water 15mm some time back which had been
in place for over 30 years leak free. I pulled at one end of the pipe
and it came straight out of the solder fitting coupler!

Yep, I've done that before! Although I wasn't actually dismantling it
till it fell apart, one was a 15mm pipe in a cupboard, that had been
there for 30 odd years and just decided to leak when a piece of wood
near it was moved!

strange things happen with pipes and water! Dont you just hate it when you
turn off the main valve, open the taps upstairs, carefully break the
connection downstairs and catch all the water - then a bit later someone
goes and flushes the toilet and all the water in the pipe to the toilet ball
valve comes rushing down out the pipe and all over the floor - grrr, never
seen that warning before!