That's the AIP ref I was aiming for, happy someone's found it.
The way I (and other controllers in my group, perhaps others in the rest of the room too, I don't know) intend it to mean is that the 250kt below 10 speed restriction is cancelled... go as fast as you like/are allowed to go below 10, but profile speed above.
If we
want you to go fast above 10 (because there's someone up your clacker), you'll get something like 'descend at maximum speed, cancel STAR speed restrictions'. In that case, it's balls to the wall, please.
And if we don't particularly care if you go fast or not (ie you're on your own in the sequence), it might change to something like 'no speed restrictions' (and I'll normally throw in the 'above or below 10' here as well, just to avoid doubt). Then it's left entirely to your discretion - go fast if you want, or maintain profile, whatever.
It does sound a bit silly to say 'cancel STAR speed restrictions' when it's to an aircraft not on a STAR, as sometimes happens, but that's how they tell us to say it.
Thanks all, interesting discussion.