If we accept that BA themselves don't do ID checks on domestic flights, how do they 'reconcile legal documents....'?
I'm pretty certain that the last time I checked-in 'manually' for a domestic flight at Heathrow the agent just brushed my photo ID aside, commenting "we don't need that."
I accept that T5's security system ties a 'face' to a boarding pass, and the reservation system will have a name for the boarding pass, but the 'name' does not have to be the 'face', unless I'm missing something.