Ken should know that the majority of pax travelling to/from LHR don't travel to/from central London. LHR's catchment area is the entire southern half of the country (and beyond).
Has Ken ever tried getting the family and luggage from a village in the depths of the west country to LHR and back by public transport? I doubt it.
I've just read an article about LHR dating fron the early 1950's in which the comment is made that, due to two major rail lines running close to the northern and southern edges of the airport (the Paddington and Waterloo lines), no doubt before long Heathrow will be tied in to the national rail network, with direct trains to all parts of the country. Some hope!
If Frankfurt, Paris CDG and even Manchester can have this kind of air/rail interchange, its scandalous that our premier airport doesn't, especially with the existing main lines running so close to the airport.
The realistic solution is to provide high-quality affordable public transport that people want to use, with proper rail/bus/air interlining facilities - something that most other European countries take for granted.