I didn't say I couldn't do it - I said it's far from convenient by public transport with anything more than a briefcase. Do you want to take luggage for a 3 or 4 week trip on the tube in the rush hour and have to make 2 or 3 changes? Getting to Paddington and changing to the HEX is similarly unpleasant. And then there are those "luggage intolerant" 5-abreast Southwest trains to Feltham followed by the public bus to the airport, followed by, yep, you got it, the tube to T4.

Until London wakes up and solves simple trips like that, people are going to be very reluctant to use public transport instead of cars.