Prawn I think was asking why the differential when it was the SAME airline end-to-end
I presume the answer lies in the murky world of cost allocation, tax and similar................
remember BA have always claimed they make no money on LHR-ABZ - when they had a higher number of business class passengers than on just about any other short haul route (those were the days eh?) - clearly costs and income were being juggled for some arcane internal purpose