thesweetcheat wrote:
I think the "second" chamber being referred to is the little eastern antechamber between the two facade slabs - on the right in this ground plan:
If that's the case , yes it's a totally different type of second chammber from Roy's , more of a court and not without precedent plus Trethevy could also have had an antechamber too same as Zennor . http://www.hobbyhorsefestival.co.uk/Guide/Cornwall/Zennor.gif
I'm not really sure this is like what is being suggested for Trethevy.