In a multi-billion pound industry where communication is vital and misunderstandings have caused fatal accidents, why does ATC still use Analogue radios? Why not move to digital like the rest of the developed world has?

I may have access to a scanner and even when sat in GF at T5, it amazes me how little an ATC has going for them with interference, regional accents and sometimes just the shear volume of communication. Having digital would also negate the interferance from those pesky businessmen turning on their mobile phones as soon as the wheels hit the ground to tell the significant other that they have landed.

Just a thought and I bet there is a very good reason why it has not happened. No idea what it is and why it cannot be overcome though given the size of the prize.