He succeeded his father in the baronetcy and to the family estates at Ravensworth Castle and Eslington Park and to extensive coal mining interests in 1791.

[4] At Ravensworth, he demolished the old 1724 house in 1808 and replaced it with a substantial mansion in the Gothic style designed by architect John Nash.

He also employed George Stephenson from 1804 at his Killingworth colliery and encouraged and financed him in the development of steam power which was vital for the improvement of the efficiency of the wagonways which transported coal from the pit to the River Tyne.

[13] He died in March 1855, aged 80,[2] and was succeeded in his titles by his son Henry, who was created Earl of Ravensworth in 1874.

[5][14] Liddell was portrayed as the character of Lord Ravensworth by actor Terence Alexander in the 1985 Doctor Who serial The Mark of the Rani.