Dear God! How utterly, utterly useless.Just received this email from TfL customer service about this issue. Here is an (obviously erroneous) categorical denial that TfL operates any National Rail services!:
Thanks for your reply on 20 June about your BritRail pass enquiry.
I’ve looked into this for you. I can confirm you won’t be able to use the BritRail pass on any of our train lines. This pass is only eligible for National Rail lines, such as Southern Rail. Transport for London do not operate any National Rail lines.
I trust that this information has been helpful.
I have pointed out this discussion thread to an appropriate person at TfL. Hopefully something will be done to rectify the multiple nonsenses that have been highlighted.