flyburg.. Talkdownman wasn't being nasty; he's a genuinely humourous guy who would not intend to offend you.. also a very good controller and a pilot too!
I too did the Heathrow job (for 31 years) and agree with my ex-colleague. CDAs are sometimes difficult to achieve from the ATC side, especially early in the morning when they use two runways for landing. It is then necessary to provide vertical separation between traffic joining both runways until they are established and one has the other in sight or radar separation exists.