Thanks so much for sharing, Ayya. As I mentioned in email, this has convinced me that in DN 2 the women surrounding Ajātasattu were indeed likely to be bodyguards. Moreover, it seems DN 2 may be the earliest evidence for this practice.
It would certainly be interesting to review the suttas and Vinaya in this light and see if any other passages might be relevant.
As I also mentioned, I found the standard of Buddhist scholarship in Penrose’s book lamentable. He says, for example, that the Buddhist taught his first sermon on the four noble truths at Bodhgaya. He uses secondary sources, citing views from American scholars with no apparent awareness of the early Buddhist texts at all. In this he follows other cross-disciplinary scholars—Thomas McEvilley and George Halkias come to mind—whose work is diminished by a lack of familiarity with fundamental source material.
I don’t think this undermines his main thesis, but it certainly doesn’t help.