Outside of Class A there is a restriction of 250 below 10000. Controllers cannot lift this rule, as it is there to protect higher speed a/c from the puddlejumpers, who may be around in uncontrolled airspace.
Some aircrew think that ATC can lift this restriction in the same way they can in class a. It is commonplace for example to ask if there is 'any speed' going into LGW, where on a Willo STAR the plate says 250kts by GWC, so that a high speed from such a distance out can be maintained if approved.