Why the railway track negative camber at Market Harborough station?

Answer 1

By "negative camber" I think you may mean the cant (or superelevation) applied to the tracks through the station (which is on a curve), making the outer rail of each track on the curve higher than the inside one.

This is to give trains a better "steer" through the curve and a better weight distribution across both rails by reducing the effect of lateral (centrifugal) forces.

Without this "tilt" to the track, all trains (in particular, those not scheduled to stop there) would have to pass through the station at a much reduced speed.

The cant is very noticeable to passengers on trains which do stop there, but normally -- on a moving train -- you wouldn't notice the effect at all, because it's expressly designed to ensure that you DON'T feel any outward lurch on curves.