I'm pretty sure the sign is non-compliant and if Greenwich contested it at the tribunal they would lose, and they currently don't provide evidence for a lot of cases anyway.
Some cases pasted below but what concerns me is why Greenwich is persisting with this.

Case reference 214012793A
Appellant xxxxxxx
Authority Royal Borough of Greenwich
VRM W583SJM
PCN Details
PCN GR02422777
Contravention date 27 Oct 2013
Contravention time 16:49:00
Contravention location Charlton Lane
Penalty amount GBP 130.00
Contravention Parked in a suspended bay/part of bay
Referral date -
Decision Date 17 Apr 2014
Adjudicator Andrew Harman
Appeal decision Appeal allowed
Direction cancel the Penalty Charge Notice and the Notice to Owner.
Reasons There is no dispute that this vehicle was parked in a suspended free bay. The suspension notice is shown in the attendant's photographs. The appellant raises the issue of signage she questioning whether the sign used by the council is compliant with the legal requirements. The council does not suggest that it has obtained the Secretary of State's authorisation for its sign and the sign used does not appear to comply with any diagram in The Traffic Signs Regulations and General Directions 2002. I am not therefore satisfied that this penalty charge is enforceable.
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Case reference 215029673A
Appellant xxxxxx
Authority Royal Borough of Greenwich
VRM WV07 USL
PCN Details
PCN GR01754658
Contravention date 28 Feb 2015
Contravention time 13:54:00
Contravention location charlton lane
Penalty amount GBP 130.00
Contravention Parked in a suspended bay/part of bay
Referral date -
Decision Date 10 Oct 2015
Adjudicator Belinda Pearce
Appeal decision Appeal allowed
Direction cancel the Penalty Charge Notice and the Notice to Owner.
Reasons
The Appellant, Dr. D. Phelps, attended before me today to explain his contention personally.
There is no dispute as to the whereabouts of vehicle WV07USL, at the relevant time, on the material date; the Enforcement Authority assert that the facility to so park had been temporarily removed, and that the said vehicle was so parked during the operative period of the suspension.
The Appellant denies liability for the ensuing Penalty Charge Notice on the basis of the prevailing circumstances and challenges as contained in his written representations, which he reiterated and comprehensively detailed at the Hearing.
The Enforcement Authority who assert that the said vehicle was so parked contrary to an operative suspension are obliged to adduce evidence to the requisite standard to substantiate that assertion.
The evidence upon which the Enforcement Authority rely to substantiate the assertion comprises the certified copy Penalty Charge Notice, extracts of governing Traffic Management Order provisions, and contemporaneous notes made by the Civil Enforcement Officer together with photographic evidence: still frames revealing the said vehicle in situ, and the applicable signage notifying motorists of the suspension.
The Enforcement Authority also adduce an annotated un-dated street-view image; this is of limited evidential value since the knowledge of the annotator is unknown and it does not add anything to the Case.
I note immediately that the sign to which the Enforcement Authority refer does not actually indicate the suspension of a parking regime or identify the extent of an area suspended; its legend notifies a manner of enforcement, which would be interpreted as implemented for inappropriately parked vehicles, as opposed to those complying with the, still visible, time plate advertising the facility to park.
Whilst I acknowledge the Enforcement Authority's comment in the Case Summary regarding the non-prescription of a suspension sign per se, nevertheless it is incumbent upon an enforcement authority to ensure that signage implementing a suspension is adequate to communicate the nature of the same to motorists. I do not find that the sign in the present case imparts a suspension.
Each Case is determined upon its individual evidential merit; I have reached my determination independently of Mr, C. Teper but I concur with his findings in Case no 2150128495.
Evidentially I am not satisfied that this contravention occurred, accordingly I allow this Appeal.
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Case reference 2150128495
Appellant xxxxxx
Authority Royal Borough of Greenwich
VRM WV07USL
PCN Details
PCN GR02349225
Contravention date 14 Feb 2015
Contravention time 13:39:00
Contravention location Charlton Lane
Penalty amount GBP 130.00
Contravention Parked in a suspended bay/part of bay
Referral date -
Decision Date 15 May 2015
Adjudicator Carl Teper
Appeal decision Appeal allowed
Direction cancel the Penalty Charge Notice and the Notice to Owner.
Reasons The Appellant has attended his appeal I find him to be an honest and convincing witness I believe what he tells me.
The Authority's case is that the Appellant's vehicle was parked in a suspended bay when in Charlton Lane on 14 February 2015 at 13.39.
The Appellant's case is that the suspension notice was neither visible nor in place when he parked in the 'Free' parking bay.
I have considered the evidence and I find this contravention is not proved because I accept the Appellant's evidence, which I find to be credible and convincing and I find that there was no suspension notice in the bay where he parked his vehicle.
Further, I have not been able to reconcile the location of the suspension notice (photographed by the Civil Enforcement Officer) and the bay in which the Appellant's vehicle was parked.
Furthermore, Enforcement Authorities now use a standardised suspension notice which has three sides. I find the 'Tow Away Zone' sign to be inadequate in the circumstances of this particular case.
The appeal is allowed.