I twist and my son does not. I consider twisting of multi-core as Sparx and also earth wires where the share a sleeve. But my son says when doing inspection and testing any twisted cables have to be undone to test and so having more stress than just the single twist and I will admit he has done a lot more domestic and inspection and testing than me.
In industrial electrics it is normal to consider there should be a hole for every wire and so with most of my life being industrial I suppose I should copy my son and stop twisting wires but a little old in the few teeth left to change my ways now.
Thanks for the replies. Sound like there's no hard and fast rule and it's down to individual preference. Modern fittings seem to grip wires very well without twisting, so that's probably the way forward for the reasons you stated.
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