Ah yes this little chestnut.
I remember being shoehorned into a smelly one on runway 20 at Brussels. Our speed control had us catching a heavy ahead (between 4.5-5 miles on TCAS also backed up by his ATC DME request). The wind strength precluded any other runway for takeoff or landing. With the traffic density at the time we had difficulty getting a word in edgeways so took the safer option of slowing down. We were less likely to cause grief to the following than the possible Wake encounter we could have sustained. And if you do the maths, from the 10 miles we were, our 15 knot reduction would have reduced the seperation (had it started at the min 4 miles) to 3 miles at least at the threshold. Still 1000' and still safer than the other option.
Yes, got a little bollocking for it and yes we should have tried a little harder to let ATC know.