The convincing source of evidence is the NSG 'the single source of truth' as well as road signs at both the northbound and southbound junctions showing as the B2089. The road used to be labelled incorrectly as the B2090 until a few years ago when a joint audit of road numbers was conducted by Geoplace, OS 7 local authorities. Where discrepancies were found they were amended with legal documentary evidence.
https://www.google.com/maps/@50.9547848,0.5058827,3a,63.6y,239.59h,83t/data=!3m7!1e1!3m5!1s1tX27nM27IN_AyFeFwFmxg!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fcb_client%3Dmaps_sv.tactile%26w%3D900%26h%3D600%26pitch%3D6.996769179456265%26panoid%3D1tX27nM27IN_AyFeFwFmxg%26yaw%3D239.58559968491633!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI1MTIwOS4wIKXMDSoASAFQAw%3D%3D

Please feel free to contact me at [email protected]

Many thanks
Jon

Hi
Thank you for the quick response - Park Lane USRN 32500330 is linked to the NSG type 3 USRN 81300031 (road number (road Number) B2089 for the whole extent between jct A21 and Vinehall Road
This is evidenced in the East Sussex County Council gazetteer which is available via find my street, a direct copy of the NSG https://www.findmystreet.co.uk/map?usrn=32500330

Regards
Jon (ex NSG custodian for ESCC)