Half Banana,
Thanks for your feedback. I managed to download a PDF of Robertson's book and I shall see what help it provides. The epub version has too many transcription errors so I will make the PDF searchable.
The GB claims to mimic the Jerusalem sect of the Jesus-movement. It came to an inglorious end in 70 CE, and probably resurfaced as the Ebionites. The Paulines ultimately succeeded, in opposition to the highly popular Gnostics. The success of the Paulines must be put down to the intervention of the Roman emperors, in which the religious fervour of Constantine's mother Helena played a big part. She initiated the gathering of Christian relics (bits of the original cross, etc.)
Search the www with: Helena Constantine relics
Doug