Call it stupid but my satnav wants to send me up Hundall Lane Old Whittingham and that looks shallower? The climb up to Norton looks challenging and worse coming back, though.
Hundall Lane?

So has my maths failed me or is that only about 4.3% average gradient?
Only? Lesser mortals, e.g. me, find that hard for two miles. Certainly causes a sweat to break out.
For what, 20 metres? Average on OSM looks like 4%.
OSM is crap. Look at it on an OS map. Canal is at 65 metres. Brim is 130 metres. Bottom of the hill rises 40 metres in about 500 metres horizontal. It's an average a little below 10% and has distinct "lips".
I might live on the edge of the fens now, but I lived at the foot of a short Mendip climb (Kewstoke Crookes Lane / Monks Hill: 600m, 12% average, 25% max) for six years and I was often very very slow but it wasn't my sweat corroding the bikes!
Bully for you. However, we're not all supermen and I, like most cyclists around here, find these hills cannot be done without exertion and sweat. Your point seems to be "I could do that easy so you must be shite"