The accident to BA038 happened at 12:42 on 17/01/2008. The first I knew about it was on going into the work canteen a minute or two after 13:00 and there it was, on the news - helicopter pictures and no information at all about what had happened.
What I'd like to know is, how do you get hold of a helicopter and pilot so quickly? - is there one always on standby for this sort of thing? -, and how actually would the news organisations find out about an event - Heathrow/BA press office, or passers-by?
You're assuming that it was a news helicopter. It may not have been.
Regular helicopters transit LHR all the time, SOP is to fly right over the runways at the 27 end. Pilots (and passengers) have mobiles. Mobiles have cameras ...
Maybe one just happened to be in the right place at the right time.