OhNoCB, my issue is that I don't use "on transition" but I use "when able" instead and nearly always pass a reason for needing a slow speed to highlight I need a slow speed. London ATC on the sectors being discussed in the first post have IAS displayed on radar via Mode S so we can see exactly what the equivalent IAS is knowing that the aircraft is flying on a Mach Number. The majority of the traffic these sectors work cruise around FL360/380 at Mach .78, and show an equivalent IAS of roughly 240kts. It surprises us how many times in the descent aircraft accelerate to 300+kts before reducing, however some others will just accelerate to 250kts and then maintain all the way down. We are also aware that the bigger jets normally show 260/270kts in the cruise at FL380/400 and either cannot reduce immediately to 250kts or are uneasy due to being close to stall, we accept that but again, cannot understand why the current 270/280 kts equivalent isn't maintained until you are able/happier to reduce to 250 kts but instead you still increase to 300+kts before pulling it back. I'm aware that the level restrictions can sometimes complicate it and that Airbus FMSs are awful at planning speed/level restricted descents, but we work and live with that all the time and can get frustrated when in our eyes, someone hasn't quite helped "the game". I was moaned at for getting a minibus a little tighter than they liked behind a very very large airbus, they came to me 12 miles in trail with the largest 4000ft higher and in front, they were both given exactly the same descent level restriction/speed/delay transmission one straight after the other and both began descending at the same time (so the minibus started down from 4000ft lower with 12 nm more mileage) yet the minibus said that they had to increase to 324kts to comply with the level restriction, however the maxibus was showing 260kts as it left FL400 and was at 250kts for the entirety of the descent from FL385 and didn't struggle to achieve the restriction at all.