Haven't a clue - maybe I should have said, I was a City ATCO up until 2003 and never once did I see the Sydenham-by-pass (one of the main arterial routes into Belfast) closed to accomodate the emergency services during an emergency.
It certainly has less than nothing to do with the Staines crash. BTW, that aircraft came down beside the A30 (near the Crooked Billet roundabout) which runs between the M4 and the Stanwell Moor Road and to my recollection, can't be seen from the M4. Yep, I used to live in Staines too!