Speed restriction @ LHR
When departing London Airports, one is generally given 'no ATC speed restriction' or 'no speed'.
This instruction allows one to increase speed to above 250 knots <10,000ft but not until passing 4,000ft AGL.
Can any bookworm quote the reference for this 'local' regulation. Doesn't seem to be in the Jeppesen Airfield Booklets.
Cheers