If it is not a daft question, if using a bus gate out to a remote stand at LHR, how does BA load (and unload) disabled pax who cannot manage stairs or are wheelchair bound (WCHS etc) onto/off the aircraft?

Do they have some form of mechanical lift (the RAF used to use a catering truck to load/unload medivac cases onto their VC10’s/Tristars) or do they have the ramped boarding apparatus like this:





If using a ‘lift’ do they put it on the right hand side and load the passenger through the ‘catering door’ to save having to remove the steps and only then load on the disabled passenger (after the steps are removed)?

Or do they ensure aircraft with 'pre-warned' non-ambulant pax go to gates with jet-bridges?

Many thanks