Climbing away from the A23 towards Pollards Hill
London Road through Norbury is a heavily used red route with bus stops, traffic lights and frequent queues, and it is lit accordingly. Sitting in that traffic tells you nothing useful about your headlamps. The roads that do are the ones climbing west and north: Northborough Road towards Pollards Hill, the streets up to Pollards Hill Park at the highest point west of the Norwood Ridge, and the roads along the edge of Norwood Grove and Streatham Common. Those are darker, 20mph, narrow and parked on both sides.
On a road like that your dipped beam is doing all the work, and a lens that has oxidised to a yellow-brown haze simply does not deliver. The pattern loses its cut-off, light spills upwards where it dazzles rather than forwards where it helps, and the usable distance drops noticeably. The same scatter is a nuisance on the A23 itself, because a blurred beam from a queue of oncoming traffic is what makes a wet night on a red route so tiring.
People usually come to us for one of three reasons: an MOT comment about the lamps, a car that looks tired from the front when it is otherwise tidy, or the realisation that night driving has become harder work than it used to be. All three have the same cause, which is the thin ultraviolet hard coat on the outside of the lens wearing through and the polycarbonate beneath beginning to oxidise. It is a surface problem, and surface problems can be machined away and resealed.
What we will not do is polish a lamp that cannot be saved. Condensation inside the unit, a reflector whose coating has burnt or peeled, a damaged projector or a crack through the lens all rule restoration out, and we check for those before quoting. If the surface is the issue, it is masking, wet sanding through the grades, machine polishing, a UV-stable clear coat and a beam check. The drive over is the A23 to the Lombard roundabout then west across Mitcham Common, about 18 minutes.