AndyH52 - You presume that I oppose the principle of airport operators paying a contribution to surrounding public infrastructure. Not so. MAG made a significant contribution to the cost of constructing the recently-opened Airport Metrolink line. I am searching for up-to-date figures, but I believe MAG's input was around £50M. The document I found is about five years old, so it could have been more in the final reckoning. This is an initiative with which I wholeheartedly approve, as I approve of subsidies provided by MAG to local bus services also. There has been no need for me to be seen calling for MAG to invest in surrounding infrastructure because they actually do.
I am well aware that HAL will be called upon to contribute to funding supporting infrastructure in the area surrounding LHR. As indeed they should. The problem is that the numbers are so large that even after HAL contribute their prescribed share, the remaining burden on the taxpayer will still be enormous - well into the billions of pounds.
I remind you that the total budget for the SEMMMS road is £290M, note the 'M' there as opposed to a 'B'. And the project has been delayed for almost 30 years before receiving approval even at that modest price. How many publicly-funded projects has London and the SE been awarded in the meantime, several costed in the multi-billions? I do not oppose private investment in public infrastructure; I welcome it. I do not oppose publicly-funded investment in infrastructure; I welcome that too. But it has to make sense financially and provide a healthy ROI. And it needs to be distributed equitably across the UK as a whole, which is lightyears away from the reality over recent years.
I note your reference to 'revenues'. HAL incurs operational costs too. In 2013, Heathrow declared a profit of £426M (before tax). Note that 'M' - it is not a 'B'. Just how much additional debt do you believe it is wise for them to take on, especially in support of just a 50% increase in business? There is a cut-off point beyond which this expenditure defies common sense, and I suspect it is well below the costs being quoted for the R3 proposal.