I wrote what cp879 wrote which was asking for a copy of the traffic management order
Dear City of Westminster,
I have sought the traffic order for this restriction on your website but have not been able to locate it. The blue sign mentioned on the PCN is prescribed by Schedule 14 of the Traffic Signs Regulations and General Directions 2016, and it is subject to General Direction 28 of that Schedule, which provides that "The signs may only be placed to indicate the effect of an Act, order, regulation, bylaw, resolution or notice which prohibits or restricts the use of the road by traffic".
Would you therefore please provide a copy of the Traffic Management Order that imposes this restriction.
Yours faithfully,