Businessman, political fundraiser and writer;

Businessman, political fundraiser and writer;

Born: May 14 1942; Died: January 17 2014.

Lord McAlpine of West Green, who has died aged 71, was a scion of his family's construction dynasty and a political activist. He was also a bewildering number of other things besides: a successful businessman in his own right; the principal fundraiser for the Conservative Party under Margaret Thatcher, before defecting to Jimmy Goldsmith's Referendum Party, which he briefly led; a tireless collector of everything from hats to Rothko paintings, and police truncheons to wives; a gallery owner; a gardener; owner of a B'n'B in Puglia; an entertaining writer and, in later years, the object of false allegations of child abuse that led to the resignation of the director-general of the BBC.

Despite his having raised, it was estimated, more than £100 million for the Conservatives during his time as its treasurer, Alistair McAlpine's loyalty was emphatically towards Lady Thatcher personally, rather than the Tories. After her fall, he made little secret of his contempt for some other members of the party, and his unhelpful (from Central Office's point of view) gripes about Michael Heseltine, John Major and William Hague eventually became outright attacks.

He called for Douglas Hurd to resign as foreign secretary, and described Jeremy Hanley, the party chairman, as a "completely useless pantaloon". In 1995, he said dismissively of John Major that "he's never done anything to me personally, except stuff up the Conservative Party" and that the Prime Minister was merely "hanging around like a pair of curtains". Having expressed his view that the Tories should lose the next election and after chairing the Referendum Party's conference, he lost the Whip in October 1996.

Although he became its leader after Goldsmith's death the following year, the Referendum Party was soon wound up. In truth, McAlpine was never really a natural politician himself. His own views were too eclectic and unpredictable and, while he was a champion schmoozer of rich sympathisers, he had very little instinct for diplomacy.

The child abuse accusations came after the BBC's Newsnight ran an investigation which implicated "a senior Tory" in assaults at a children's home. Though the programme did not name McAlpine, he was soon mentioned on social networking sites, with both Sally Bercow, the Speaker's wife, and the journalist George Monbiot identifying him.

It quickly emerged that the victim had not been shown a picture of McAlpine, and quickly conceded that he had not been his abuser. When it emerged that Newsnight had not approached McAlpine before airing the accusation, George Entwhistle, the BBC's newly appointed director-general, resigned.

Both the BBC and the ITV programme This Morning, which had followed up the story, paid substantial damages; Monbiot agreed to undertake work for charities. Mrs Bercow denied libel, but the courts found against her and she too settled. McAlpine gave the money to charity and agreed not to pursue Twitter offenders with fewer than 500 followers if they donated £25 to Children in Need.

Robert Alistair McAlpine was born on May 14 1942 in the Dorchester hotel in London, which his family had built and owned. He was the third child of Lord McAlpine of Moffat and his wife Molly (née Garnett), and the great-grandson of "Concrete Bob" McAlpine, who founded the family business and built the West Highland Railway. Alistair (as he was known) went to Stowe, but found school difficult and left at 16. In his twenties, he was diagnosed as dyslexic.

He immediately went to work for Sir Robert McAlpine Ltd, starting in 1958 on a building site in south London, learning the business from the ground up. After five years, he became a director, but he also began to generate a fortune of his own.

McAlpine's first political excursions were campaigning for British industry to sign up for the Common Market (a position Sir James Goldsmith also backed then, despite the pair's later opposition to the European Union). He had, however, no particular party allegiance until he encountered Margaret Thatcher at a dinner in 1975.

He was at once bowled over by her, and agreed to become the party's unpaid treasurer. He set about his task with gusto and considerable flair, lavishing hospitality on rich businessmen and talking up the party's "pro-business" stance with journalists. An instinctive bon vivant and gossip, McAlpine's innate charm and genuinely wide range of interests soon had money flowing into the party's coffers. He was Deputy Chairman of the party from 1979-1983 and in 1984, he became a life peer; at the party conference that autumn he was in the suite directly above Mrs Thatcher's when the IRA bombed Brighton's Grand Hotel.

In 1987, he underwent a major heart operation and moderated his lifestyle. In 1989, his own business interests hit the rocks, and he suffered considerable losses. The following year, he resigned as Tory treasurer, sold almost all his possessions and moved abroad, in part because of threats from the IRA. Weeks later, his former house was bombed.

For the next decade he concentrated on journalism and on writing books. He turned out pieces for newspapers and magazines such as The Spectator on modern art, his mania for collecting trivia, and his growing antipathy towards the EU, as well as his memoirs and books on politics and collecting.

After the Referendum Party folded, in 1999 McAlpine had another bypass operation, which necessitated a tracheotomy and put him in a coma for a month. Upon recovering, he became a Roman Catholic and - somewhat inconsistently - got divorced. In 2002, he embarked on his third marriage, to Athena Malpas, who was three decades younger than him, and lived with her in Puglia, where he cultivated his garden and took occasional paying guests.

He was first married, in 1964, to Sarah Baron, with whom he had two daughters. They divorced in 1979 and he the following year he married, secondly, Romilly Hobbs, who had been his political secretary, and with whom he had another daughter.