The Earl of Onslow: Colourful hereditary peer who advocated reform of the House of Lords

It is a measure both of Michael Onslow's courage and tireless sense of duty that within weeks of his death from cancer he was still active in the Lords; his last speech was made only three weeks before he died. Paradoxically, although he served it well, he thought the House of Lords was well past its sell-by date.

Indeed, in 1979 he had urged Margaret Thatcher to reform it rather than leave the task to a Labour government. He anticipated that the latter would do it stupidly, as indeed it did.

The stories about Onslow are legion and, more surprisingly, most are true. He did pursue a bullock down the A3 on horseback and he also acquired an authentically Roman stone testicleto put under his wife's pillow. He inherited the earldom and the family estate in 1971 and confessed himself only too glad that Clandon, the family pile, had passed into the hands of the National Trust: the family had been "slaves to the servants". He was quite content to farm the 800 acres left to him and to attend the House of Lords. He sat loosely to the Conservative cause, once memorably telling the Daily Telegraph that he did not know what Tory policy was "on virtually anything", adding, "And I'd probably disagree with it if I did."

He had a dry wit and a trenchant turn of phrase. Taxed with beingliberal on homosexuality on thetelevision programme Have I Got News for You, he remarked that it was fine if the boys got together, less good if the gym master gets involved. Most of what he had to say concealed, robust common sense behind a slightly whimsical way of voicing it. Attacking apartheid, for example, he pointed out that "in Egypt the man in a mud hat on the Nile can dream of being a fat cat, but there is no such dream for a black South African – he cannot aspire to being white."

Michael William Coplestone Dillon Onslow was born on 28 February 1938, the eldest son of the 6th Earl, who had been a more orthodox Conservative, serving as deputy Chief Whip in the House of Lords in the Churchill, Eden and Macmillan administrations. Onslow was educated at Eton and the Sorbonne. He joined the Lifeguards and served with them in Aden and Oman. While there, he discovered a flair for photography and in 1960 took it up professionally. Two years later he moved to the City, his arrival signalled characteristically by the loss of his pet monkey on the Tube. The police had to retrieve it.

Once he had succeeded to the title, he was tireless in attending the Lords and sharp in expressing his views. Nevertheless he believed strongly that the House was an anachronism. "I have been in favour of Lords reform almost since I've been there," he explained, "because any House which has me in it really needs to have its head examined." Some thought it inconsistent when he opposed Tony Blair's plans to replace it, but he had not changed his mind. He thought it wrong that he had power over fellow citizens because his forebear had got tight with the Prince Regent, but he was against sending the peers packing when there was no agreement on what was to be put in their place. "If the Government is going to play 'silly monkeys' I'm going to behave like a football hooligan and bitch things up", he said.

His preference was for a House that was two-thirds elected. But when Lord Cranborne stitched up a compromise which kept 92 hereditary peers in the Lords, Onslow conscientiously abstained and then stood for election. His fellows chose him to be one of the surviving hereditaries and he was given to teasing appointed peers on the grounds that he had at least been elected to his position. While he deplored the 1999 Act as a "weak half-bastard thing", he claimed, in a Guardian article, "to be a pustule on the rump of the body politic to remind Mr Blair of unfinished business."

Away from the House, Michael Onslow achieved some prominence in the tradition of English eccentricity. Chosen in 1994 to present a series of programmes on Radio 3 devoted to hip-hop, ambient house, acid jazz and thrash metal among other things, he began: "Hello and welcome to the Supertunes chill-out zone from me, Lord Onslow, your mellow and, I hope, laid-back host," and his enthusiasm proved infectious. He was to appear twice on Have I Got News for You and had to remind his hosts in 1999 that he was not his cousin, Cranley, a far more weighty figure on the political scene. Ian Hislop was particularly taken and ensured a second appearance some years later, in 2007.

He hunted with the Fernie and organised a shoot on his own estate, but his love of the country was accompanied by a series of episodes that, embarrassing or not, kept his name in the public eye. He rode his stallion, Miltiades, into a bog from which he had to be extracted by a mixture of police, firefighters and passers-by. Shortly afterwards he rode the horse to the help of an embattled nude model, Vivien Neves, locked in conflict with the local authority after her house had been damaged by a lorry. She rightly described him as "a brick". In 1985 he was ousted as President of the Open Spaces Society because he supported the army's right to train on Salisbury Plain.

Although he could be very funny about his ancestry – the Earldom had been a bribe to secure a previous Onslow's support for the Act of Union with Ireland, his earlier ancestors had been cattle thieves – membership of the House of Lords gave Onslow the confidence to express his views and a platform from which to air them. Beneath the charm and the somewhat raffish appearance lay a good deal of shrewdness and the occasional hint of steel. He could be deeply serious about things that mattered. "My father started his war service in Egypt in 1941 aged 28 and ended it in 1944 when he was captured at the Battle of Villers-Bocage. He had 13 tanks blown up underneath him in that time. I do not think that he ever went to bed sober," he told the Lords when discussing stress in battle. "He died extremely young, at the age of 57. Sometimes I worry and ask myself whether I began to understand him, and the answer is no, I did not."

Pursuing somewhat Whiggish views, he was critical of racism in the police and army, and he sided with the farm workers' union when he condemned rogue employers who ousted them from their "tied cottages" and promptly sold them on for a large sum as second homes. He argued that Ian Smith's actions in Rhodesia were tantamount to treason.

If at times he took an unfashionable line, it was never without a great deal of knowledge. He fought the Thatcher government's Wild Life and Countryside Bill with a passionate seriousness that left little room for wit. He was also capable of considerable pertinacity. He found it hard to believe that when an intruder broke into the Queen's bedroom, he could not be prosecuted. It seemed to him absurd that had the intrusion been into the Russian embassy, a prosecution would have been in order. Hence his bill to create an offence of criminal trespass, which he took through all its stages in the Lords, but for which no time could be found in the Commons. In his final years in the House, he was appointed to the Joint Committee on Human Rights and proved an eloquent defender of individual rights.

He attended the House almost to the end, confined to a wheelchair and suffering from cancer. But it did not prevent him from speaking his mind. His final speech was devoted to savaging the Coalition Government's attempt to impose fixed-term parliaments. Suggesting that it had gone "completely doolally over constitutional change", he added that in three decades in the House he had regarded himself as a disloyal Conservative – "and I will go on being a disloyal Conservative. If they are doing something that I believe is as fundamentally wrong as this, I will say so." There could be no better epitaph.

In 1964 Onslow married Robin Lindsay, daughter of Major Robert Lee Bullard III of Atlanta, Georgia and Lady Aberconway. They had one son, Robin, who succeeds to the title, and two daughters.

Michael William Coplestone Dillon Onslow (Earl of Onslow), farmer and politician: born 28 February 1938; married 1964 Robin Lindsay (one son, two daughters); died 14 May 2011.