wrote

Any surface-mount cable should be in trunking to comply with wiring
regs of course.

Is that strictly the case here?
The OP says that the cable is clipped to the ceiling.
If this is the only exposed bit of cable, isn't the ceiling the least likely
place for something to get damaged and therefore not requiring mechanical
protection? (Yes I know it would be more aesthetically pleasing to have
white trunking rather than grey T&E across the ceiling).

Phil