I have already replied to the OP on Pepipoo as follows:-
Transport for London does not have approval for a suspension sign therefore this PCN is unenforceable IMO.
Case reference 2180309331
Appellant Richard Mills
Authority Transport for London
VRM GC16AEY
PCN Details
PCN GF68259162
Contravention date 09 Apr 2018
Contravention time 15:46:00
Contravention location
Victoria Embankment
Contravention: Stopped where prohibited on red route or clearway
Decision Date 15 Sep 2018
Adjudicator Anthony Chan
Appeal decision
Appeal allowed
Direction cancel the Penalty Charge Notice and the Notice to Owner.
Reasons
The Appellant attended in person.
The Appellant made several points one of which is that the suspension sign is not authorised. There may be
an issue as to whether such a sign needs to be authorised but the Authority's case is that the sign is
authorised. That being the case, the Authority must provide evidence of the authorisation. It has not done so. I
allow the appeal.
OP I doubt you were in the parking bay anyway but on the DRLs, ask for the video :-
https://www.google.com/maps/@51.4778849,-0....i8192?entry=ttuI would send the following reps:-
Name
Address
VRM
PCN Number
I challenge liability for PCN


? because the contravention alleged did not occur. Penalty charges can only be imposed by signs authorised under section 64(2) of the Road Traffic Regulation Act 1984, this means either signs authorised by the Traffic Signs Regulations 2016, or by signs specifically authorised by the Secretary of State.
The Traffic Signs Regulations 2016 do not authorise any parking suspension signs, and a search of the Department for Transport website at
https://www.dft.gov.uk/traffic-auths/ indicates that Transport for London has not obtained a special authorisation from the Secretary of State for the use of any parking suspension signs.
In the absence of a lawful parking suspension sign, the contravention alleged cannot have occurred.
Yours
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Mike