Whatever the incompetence or inefficiency of Heathrow's snow clearance strategies, the reason for the annual snow debacle is simple. It is the white elephant that nobody in the media has mentioned.
If you are running an airport at 99% capacity, any delays caused by runway snow clearance or de-icing aircraft will lead to delays which will increase exponentially the longer the conditions persist.
The politicians and general public are quite happy to run Heathrow at 99% capacity but these delays are the inevitable consequence of the misguided policy to cancel any airport expansion in the south-east of the UK.