CAA have issued an Emergency Mandatory Permit Directive on all permit aircraft carrying Martin Baker ejection seats with scissor shackle mechanisms..

Emergency MPD 2011-008-E: Martin-Baker Aircraft Company Limited: Inspection of Ejection Seat Drogue Shackle Connection to Scissor Shackle

That will be a few classic jets grounded until that is done, plus the tin triangle too.

It also explains why the parachute didn't open in that Reds incident, last week. Still doesn't explain why the seat went bang in the first place.