On the CF104 we used to put A4 envelopes full of cut up strips of foil(one shot chaff!) in the speed brakes both sides. (A hazardous job for the groundcrew as it was done after start).
Quite often we would not use this ECM! and with the standard practice of popping the speedbrake on short finals the locals would get hacked off with their Spargel fields full of foil.
The question is why was the speedbrake put on the Harrier in the first place? (Other then Hum's reasons). It was only after it was put their that someone found a use for it. Wonder where we have heard that before.