I was just browsing and ended up in my own post through Google.. just wanted to help you out with the speed limit at Richmond park...here's a link to the 2010 amendment...
http://www.legislation.gov.uk/uksi/2010/1194/made
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Citation, Commencement and Interpretation
1. (1) These Regulations may be cited as The Royal Parks and Other Open Spaces (Amendment) etc. Regulations 2010 and shall come into force for the purposes of regulations 1 to 4 on 6th April 2010 and for all other purposes on 1st October 2010.
(2) In these Regulations–
“parking permit” means a permit issued by or on behalf of the Secretary of State for the parking of a vehicle;
“parking place” means a place shown on a notice exhibited by or on behalf of the Secretary of State as being appointed under these Regulations as a place where a person may park a vehicle; and
“vehicle” means a mechanically propelled vehicle intended or adapted for use on a road.
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I hope it helps you to understand the speed regulations of Richmond Park. You're welcome