He was oldest son of Adam Leng of Hull, and Mary, daughter of Christopher Luccock, of Malton, architect.

During this period, he contributed anonymously to the Hull Free Press, calling for reforms such as slum clearance and ship safety.

His brother John Leng retained these beliefs, but William joined the Church of England and became a supporter of the Conservative Party.

[1] In 1864, Leng became managing editor and joint proprietor of the Sheffield Daily Telegraph with Frederick Clifford.

[1] Politically, he was a supporter of imperial preference and established Conservative Clubs and electoral organisations on a constituency basis throughout Sheffield.

[1] He married in 1860, Anne (died 1893), daughter of David Stark of Ruthven, Forfarshire, and widow of Harry Cook of Sandhurst, Australia.