As the authority were foolish enough to put their ignorance of LATOR in the NOR, IMO they haven't a hope in hell at adjudication.
LATOR were made by the Secretary of State pursuant to powers in the RTRA, they therefore import the definitions and meanings of 'traffic signs' in the Act:
64General provisions as to traffic signs.
(1)In this Act “traffic sign” means any object or device (whether fixed or portable) for conveying, to traffic on roads or any specified class of traffic, warnings, information, requirements, restrictions or prohibitions of any description—
(a)specified by regulations made by the [F1relevant authority] , or
(b)authorised by the [F1relevant authority] ,
and any line or mark on a road for so conveying such warnings, information, requirements, restrictions or prohibitions. (a point made by others in this thread).
(my emphasis)
IMO, the debate has moved on from whether the road markings were adequate, although this could still be put forward, it's their failure to give proper consideration to your reps because of their use of the wrong legal context - see paras 2 and 3 on p2 of the NOR from to 'I have noted.to...guidance'.