Javelin
The 180kts to 160kts reduction is used to fine tune the spacing to cater for errors in vectoring etc; this avoids lost space on the approach. Trouble is of course that the position for that reduction to take place varies depending on the vectoring and how long the final is.
One of the advantages of using a long final (say 15nm) is that the spacing should be established by about 10nm from t/down meaning that you should receive the 160kts to 4d instruction quite early. The worst possible scenario is the short final, where the director is fighting not to lose time on the approach and so keeps the speed on as long as he dare - leading to hot approaches.
(Personally, my view is that traffic should be permitted to reduce from 180kts by 7nm at the latest, 8nm if it is a heavy, regardless of whether the spacing is correct.)
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