Who is Mr. Wansborough from The Woman in White and what is their importance?

Mr. Wansborough is the son of the old Welmingham church vestry clerk. He lives in nearby Knowlesbury, where he keeps the duplicate church registry locked in a vault. Wansborough helps Walter uncover the fraudulent entry in the original registry that falsifies a marriage between Sir Felix Glyde and his companion, Cecilia Jane Elster of Knowlesbury.