[1][2][3] Selwin-Ibbetson unsuccessfully contested Ipswich in 1857 and 1859[1] but in 1865 he was successfully returned to Parliament as one of two representatives for Essex South.

[1][4] In 1867 he resumed by Royal licence the original family surname of Ibbetson in addition to that of Selwin and the following year he succeeded his father in the baronetcy.

When the Conservatives came to power in 1874 under Benjamin Disraeli Rookwood refused the office of Chairman of the Committee of Ways and Means (Deputy Speaker of the House of Commons).

Disraeli instead appointed him Under-Secretary of State for the Home Department, a position he held until 1878, and was then Financial Secretary to the Treasury from 1878 to 1880.

[9] His estate comprised some 4,000 acres, coal mines in Durham and Yorkshire, and a considerable quantity of house property in Halifax.