The following was posted on a forum of the flight crew website on 02nd Mar by our ATC Liaison Pilot:
London Terminal Control will commence a speed limit trial affecting all departures from London TMA airfields from 8th April. Simply stated: your speed will be limited to 250Kts or min clean speed, whichever is higher, until passing FL100.
All that you will notice is that ATCOs will not issue the instruction "no ATC speed restriction" on departure other than (exceptionally) for tactical reasons.
Still waiting for 'official' notification from The Management.