The regulation is absolute, not dependent on where it is, however engineering judgement can result in C2 or C3 based on how dangerous it is in an EICR, hence my follow up post:I get it If it’s in an escape route C2 but in a bathroom of a domestic property?
but as always I’ve not seen it so cannot say with any certainty
If its a long route in a bathroom it could obstruct entry/exit from the bath/toilet/door etc, so that would be a C2 , if a short length in a corner out of harms way - ok for C3No.
If the failure to support against premature collapse could represent a danger, then C2, but if its out of harms way, it would be C3.
Both would be unacceptable for a new installation though.
But if the trunking's original glued backing has failed so you replace that with more glue, you still haven't changed anything!
It was a C2/C3 because it had no protection against premature collapse and it would remain exactly the same because it still has no protection against premature collapse, so the same coding!