Honestly not me, but a friend did a CU change and cut the seals to remove the cut-out fuse at around 09:00 and within the hour, a DNO van and man turns up at the address.
He wanted to know what was going on and my friend, the charmer he is, ended up promising to follow the man's advice to get a DP isolator fitted before doing his next CU change and that was all.
Fortunately the home owner wasn't there to witness the goings on.
Oh, and as you have already worked out, it was a Smart meter........
Regards
BOD