Yes, I'm making that assumption. However, since the trunking was not very firmly attached to thee wall, I was more-or-less able to satisfy myself that such was not the case I would add that relatively little of the wiring in the building is 'buried in walls' - which may or may not be related to the fact that it is a listed building.You're assuming that a cable does not go through the wall into or out of the trunking.
However, I'm reminded of that first thing I was taught in my further education (that "common things are common,and rare/obscure things are rare"), a variant of which is "the most likely/'obvious' explanations are more likely to be correct and more obscure ones". In this context, I still think it is most likely that things are 'just as they seem' - i.e. a socket fed from a lighting circuit (be it 6A, 10A or 16A) with flex from a ceiling rose - a (compliant) situation (provided the flex CSA is adequate) about which I would personally have few, if any, concerns.
Kind Regards, John