I just happened to wander into the garden 30 seconds before the detonation. Very very loud bang (preceded by 1 much quieter one). Especially at 6am on a Sunday, before the world had roused. There was a thin dust cloud visible a few minutes later; it didn't hang around much.
PAC said he heard it in Tilehurst (which is virtually Reading, nearly 20 miles away).
I went to have a nose later from the cyclepath alongside. There is now too much vegetation to see the rubble. It was quite sobering thinking about the construction workers.