Henry Pelham-Clinton, 4th Duke of Newcastle

On 22 March 1821, Newcastle published a pamphlet in the form of a letter to Lord Liverpool, protesting against a Bill for Catholic Emancipation. Newcastle argued that if his government supported Emancipation they would be doing the country an injustice for two main reasons. Firstly, the attention of the nation was preoccupied with domestic problems and little interested in the question, so to pass Emancipation now would be a betrayal. Secondly, the government could not be neutral on this question because if the Bill passed Parliament, the King would have to refuse Royal Assent as it would be in breach of his promise, made in the Coronation Oath, to uphold the Protestant constitution. If the King were to do this without the advice of his ministers then it would be unconstitutional since the King could only act on the advice of his ministers. Thereby the government should adopt a position on the question, and this position should of necessity be opposed to Emancipation.[2]

He did not hold any national office but he was extremely active in politics. From about 1826 he became one of the leaders of the so-called "Ultra-Tory" faction, staunchly supporting the traditional establishment of Church, Country and State. He rejected the label of Tory, however.[3]

On 13 March 1827, Newcastle told Lord Colchester that he wanted to form a group to support the King in forming a government opposed to Emancipation with the aid of Lords Mansfield, Salisbury and Falmouth, and that he could win the support of about 60 peers.[4] On 24 March Newcastle had an audience with the King, George IV, on the question of Emancipation. However early in the conversation, the King interrupted Newcastle, "it was only occasionally that I could edge in my remarks & opinions". Newcastle said himself and other peers' wishes for an administration "formed on anti-Rom. Cath. principles & that if it would be H.M.'s pleasure to form such an administration it would be certain of support & success". The King, however, said a Prime Minister could not be appointed until it was certain that Lord Liverpool would not recover from his stroke.[5]

Newcastle responded by saying this delay could only help the pro-Emancipation politicians and that he and other peers would help the King in his choice if he would choose Protestants, "not doubtful Protestants but such as are staunch and unequivocal in their opinions". The King replied: "That you may safely rely upon". When Newcastle was going to suggest Lord Eldon as Prime Minister, the King stopped him by saying Eldon was persona non-grata and suggested Wellington instead. Newcastle was opposed to this choice and wanted the King to make a stronger declaration in favour of a government opposed to Emancipation. The King was annoyed at this and asked, "What more can I do?" Newcastle said nothing could be better than his declaration and that if he had the permission to make the King's declaration publicly known. The King would not allow this, however.[6]

Newcastle wrote to Lord Colchester on 15 January 1828, that he wanted "a sound, plain-dealing Protestant administration, devoid of all quackery and mysterious nonsense".[7] The Duke of Wellington sought Newcastle's support for his new government, and when he learnt that it did not possess Newcastle's confidence (and not receiving a reply to his first letter) he wrote again to him on 31 January, saying: "Nothing can be more unpleasant to me than that the friendly Relations between your Grace and the Govt. should be suspended". Newcastle finally replied on 4 February, saying his government did not possess his confidence.[8]

On 18 September 1828, Newcastle condemned the government for "neutrality, conciliation, and modern liberality". Wellington "may be the victim of a monstrous error" but he had supported relieving the Dissenters and his first parliamentary session was "by far the most disastrous of any in the memory of man". Newcastle advised that those opposed to Emancipation "must unite in Protestant associations from one end of the country to the other, and as Parliament is not sitting, they should address their Protestant King". Failure to do this might provoke punishment from God.[9]

Newcastle led a crowd to Windsor to petition the King against Emancipation. One contemporary Canningite called it "radical all over".[10]

When in October 1829, Newcastle was criticised for evicting tenants who had voted against his candidates, he famously wrote: "Is it presumed then that I am not to do what I will with my own?".[11] He repeated this in the Lords on 3 December 1830.[12] In response to further evictions, The Times rebuked Newcastle for acting like the recently deposed Charles X of France in abusing his power and claimed that his actions were the best argument in favour of reform.[13]

Pelham-Clinton was a vehement opponent of electoral reform. This stance led to attacks on his property during the Reform Bill Riots of 1831. Nottingham Castle was burnt to the ground and his residences at Clumber Park, Nottinghamshire and Portman Square, London also had to be fortified against the mob.[1]

In 1839, Newcastle objected to the appointment to the magistracy of two gentlemen nominated by the government, but of whose political and religious principles he disapproved (being Dissenters).

He wrote a very offensive letter to Lord Chancellor Cottenham, and on his refusing to withdraw it he received a letter on 4 May from Russell informing him that the Queen had no further occasion for his services as Lord Lieutenant of Nottinghamshire. Charles Greville wrote in his diary on 2 May:

I met the Duke of Wellington at the Ancient Concert, and asked him the reason, which he told me in these words: "Oh, there never was such a fool, as he is; the Government have done quite right, quite right, they could not do otherwise".[14]

The papers of the 4th Duke, including his very detailed personal diaries for the period 1822–1851, are now held by Manuscripts and Special Collections at the University of Nottingham.[17][18]