If, as people seem to be saying/assuming, that isolator has been installed upstream of the meter, has anyone ever seen that done before? In my limited experience, I certainly haven't.
Whilst such a practice would make life (slightly) easier for those changing the meter, and would provide a means of isolation, it would not enable the 'tails' to the CU to be changed (e.g. for longer ones, if a new CU were in a different position or had its incomer 'at a different end' etc.) without breaking the meter seals - and the ability to do that is at least one of the potential reasons why people may request that an isolator is fitted. I suppose, give the isolator, one could always extend the tails using Henleys or suchlike, but that's something that I personal would prefer not to do if it were 'unnecessary' (if if no 'branching' of the tails was required).
It has never even occurred to me that isolations requested by a consumer might sometimes be installed upstream of the meter, and had I seen that happening when mine was installed, I would certainly have done all I could to persuade the person concerned not to do it that way.
Kind Regards, John