I would like to make two points.
1.
If you look at the Jepp Plates for Brisbane Australia, it has a simple Loss of RT proceedure. It actually gives a phone number to ring on your mobile. You get straight through to the SATCO and the problem is resolved.
2. I was flying a VC8 (Viscount) from Southend to Manchester a few years back and had a total loss of R/T after being handed over from Southend Tower to London. We couldn't raise anyone. Not even the previous (Twr) frequency. So after trying every frequency in the book and then some,we just sqwarked 7600 and continued all the way to Manchester, went around the hold once and did a full procedure ILS and landed. Afterwards we landed and phoned the Tower at EGCC. They said there was no problem at all. They figured our R/T had failed and watched us on radar do exactly what they expected us to do. Everyone was warned and room was made for us.
The point I'm trying to make is that if you have a genuine R/T failure, ATC can handle it and ensure that you safely conclude your flight.
But if Mr Darling thinks that it is possible for EGLL or any other major airport to operate without R/T, then perhaps he should try to explain why it is mandatory to have radios in aircraft operating into these airports in the first place.