Muddied by the fact that certain areas of the UK CAA misinterpreted ICAO Doc4444 a few years ago and mandated that as well as applying time-based wake turbulence departure separations (which states there is no departure wake separation required between two Heavies), airports should also apply a 4nm distance-based wake separation between Heavy aircraft.
Thankfully we've moved to RECAT EU so can forget that.
Not the CAA's finest hour.