Born at Edinburgh into a family with prominent connections to the mining and agricultural interests of Northumberland, Liddell was the eldest son of Henry Thomas Liddell, who had sat as a Tory member for the county, 1826-30.
Liddell attended steadily in his first parliament. He was present for 111 out of 254 divisions in 1853, and for 98 out of 198 in 1856.
Returned unopposed at the 1857 general election, he explained on the hustings that although he had been absent from Cobden’s censure motion on ministers over Canton, he considered their conduct to have been ‘ill-judged’.
Following his unopposed return at the 1859 general election, he contributed to the debate on the address by protesting that Palmerston’s foreign policy was ‘always alarming and often intrusive’ and that his influence was ‘destructive’ to European peace, 9 June 1859. In an extensive speech, he soundly attacked Palmerston’s ministry for its interference in Chinese affairs, 15 May 1863, and argued that the government was ‘attempting, by very doubtful and illegal means, to prop up a power they themselves had destroyed’, 6 July 1863. His subsequent resolution that ‘further interference on the part of this country in the civil war in China is impolitic and unnecessary’ came to nothing, 22 Apr. 1864, and he later vilified Palmerston for his ‘glaring inconsistencies’ in explaining the ministry’s policy towards China, 20 May 1864. He also criticised the ministry for leaving Denmark ‘in a scrape’, 5 July 1864, and was in the minority for Disraeli’s censure of government policy during the Danish war, 8 July 1864. His attitude appears to have softened a year later, however, when he praised A.H. Layard, the under-secretary of state for foreign affairs, for his ‘altered tone’, 30 June 1865.
Liddell, however, was not above supporting Palmerston’s ministry. Even though it gave him ‘considerable pain’ to ‘adopt a different course’ from his party, he backed the government’s commercial treaty with France as a means of averting war, 21 Feb. 1860. He was also a passionate defender of the shipping interest
At the general election of 1865, when he again was returned unopposed, Liddell gave muted praise to the late Liberal government, but only because it had been under the leadership of Palmerston, ‘who was a Conservative’, a mischievous comment that mirrored his recent endorsement of the ministry’s foreign policy.
Returned unopposed at the general elections of 1868 and 1874, Liddell remained an assiduous contributor to debate in the House, and on the death of his father in March 1878, took his seat in the Lords. A philanthropist, he supported the Newcastle branch of the Society for the prevention of cruelty to animals, the Newcastle aged female society, and the Northumberland village homes for girls. He also served as president of the Royal Agricultural Society, the Institute of Naval Architects and the Newcastle Society of Antiquaries. After a long illness, he died at his seat at Eslington Park in July 1903. He was succeeded by his brother, Atholl Liddell, the fifth son of the first earl, on whose death without issue the earldom expired.
