Originally Posted by KARFA

It definitely the BA policy not to ask for ID at the gate when boarding a domestic flight either at LGW/LHR or outstations.

To the extent anyone is asked for a passport at the gate it is almost always due to a passport/doc check being required for the subsequent international flight the passenger is connecting to. There aren't random checks at the gate for ID by BA (NQY was a notable exception due to "reasons" ).