OK, OK..... Before anyone leaps..... I'm old, past it and don't understand current ops.. Just to say the delays you mention were happening 10 years ago when there was NO delay at Heathrow. I was sitting around doing nothing one morning when a BA flight from Frankfurt said he was surprised at getting a straight in because he'd waited 45 minutes on the ground due to "delays into Heathrow". It's often the case that en route delays are blamed on the destination..... just like pilots telling pax that the delay is due to ATC!!!
Well, if he got a straight-in the system worked perfectly! Got a complaint over the freqeuncy some time ago from a pilot who was fed up with being grounded for 35min at an airport wich is about 25min total flying time to the airport I work (and 5 min until entering my sector). He told me that it was unheard of that he had that much delay when up in the air he got a shortcut and no speed restrictions.
What he didn't know was that 25 mins earlier the sector was completely crowded with Inbounds. And he would have been in the middle of that if he would have departed as planned. (Major speedreductions and delaying vectors would be the result)