IMO, the alleged contravention is 'Failing to comply with a restriction on vehicles entering a pedestrian zone'.
So, what's a Pedestrian Zone?
The TSRGD defines this as:
"pedestrian zone”
an area—
(a)
which has been laid out to improve amenity for pedestrians; and
(b)
to which the entry of vehicles is prohibited or restricted
I can't see that (a) is a matter for a TMO, therefore only (b) applies.
So, does the TMO provide that 'the entry of vehicles is prohibited or restricted' and is this signed accordingly?
'3. No person shall cause any motor vehicle to enter or proceed in the prescribed street....'
Seems to meet the criterion.