As Tory conference began over the weekend, David Cameron was stung by a string of headlines about Mark Reckless, the Tory MP who has followed his colleague Douglas Carswell in defecting to UKIP. With rumours abounding of more departures, and Ukip's Nigel Farage claiming the party is talking to Labour MPs as well, this could be the start of a mass exodus.

Defections aren't just exciting because they keep gossip-hungry hacks happy. They can spell death for an established party, spawn a new one, and indicate radical shifts in the political weather. Here, we've run through six of the most significant British political defections.

Winston Churchill: Conservative to Liberal, 1904

Churchill switched party three times in his political career: from the Conservatives to the Liberals in 1904, from the Liberals to an independent candidacy in 1922, and back to the Conservatives in 1924. The first of these marked a rejection of the protectionist philosophy popular in conservative politics at the time. His Oldham constituency was an important centre of the cotton-spinning industry, so for obvious reasons many of Churchill's constituents supported the duties on cheap foreign textiles supported by the Tory party at the time. Churchill defected to the Liberals as a supporter of free trade—as a young man, he was known as a maverick, whom nobody would have bet on as a future PM. When he returned to the Conservative party, though, (as he put it “anyone can rat, but it takes a certain amount of ingenuity to re-rat”) it marked a decisive shift away from the party's obsession with local issues and back toward national interests.

Oswald Mosley: Labour to New Party, 1931

Oswald Mosley, perhaps Britain's most famous fascist, spent his early career in politics as an MP for the Conservatives and then for Labour. Once Labour came to power in 1929, the erudite and well-connected Mosley hoped to secure a Cabinet position, but in the event he was given an insignificant ministerial brief as Chancellor of the Duchy of Lancaster. Mosley became increasingly dissatisfied as his radical proposals, known as the “Mosley memorandum,” were blocked by superiors and left to found the aptly titled New Party. The party's policies were a mishmash of interventionist big-state socialism and authoritarian control. Gradually, they crept towards a more extreme right-wing position and would join with other organisations to form Mosley's British Union of Fascists. Mosley's policies, a heady mix of authoritarian fascism and socialist-style protectionism, are forerunners to those later espoused by the BNP, arguably Britain's most successful far-right party.

Campbell Stephen, John McGovern and James Carmichael: Independent Labour Party to Labour Party, 1947

The Independent Labour Party (ILP) was a hard-left socialist party, which disaffiliated from the main Labour party in 1932 amid a growing divide between the ILP's class-based politics and the more tempered socialism of the Labour Leaderships of Arthur Henderson and Ramsay MacDonald. The decision was described by left-wing Labour heavyweight Aneurin Bevan as a choice to remain “pure, but impotent.” In 1947, he was arguably vindicated when the ILP's only three MPs, Campbell Stephen, John McGovern and James Carmichael defected to Labour, effectively sounding the death knell for the ILP as a significant political force. The end of the ILP brought an effective end to tub-thumping socialism in mainstream British politics until the 1980s.

The “gang of four,” Labour to Social Democrats, 1981

Roy Jenkins, a former Cabinet Minister, and his three Labour colleagues David Owen, William Rodgers and Shirley Williams, founded the Social Democratic party in 1981. At a press conference, they pledged to “reconcile the nation” and “heal divisions within classes.” Forming an alliance with the Liberal party later that year (this would eventually lead to the current combined Liberal Democrat party), the party attracted significant attention throughout the early 80s. They won several by-elections with a strong network of grassroots activists and a mission to reform politics, but failed to break into serious power as questions were raised over their ability to govern and their internal divisions. Remind you of any parties today?

Robert Kilroy-Silk, Ukip to Veritas, 2004

If you think the rightward territory of British politics is a bit weird today, it's worth remembering the temporary prominence of a certain perma-tanned talk show host. As a young man, Kilroy-Silk was a Labour firebrand who once insisted that “Labour must always be a class party, for it is a class war we are fighting.” Later, as well as presenting the sinister talk show Kilroy, Kilroy-Silk found time to be elected as a Ukip MEP, and expressed ambition to lead the party. When it became clear this wasn't going to happen, he founded his own party, Veritas (meaning truth), which had little discernible policy other than opposing the other parties' “lies and spin.” The whole affair, and the inevitable media attention it attracted, marked an arguable nadir for Ukip prior to its current meteoric rise.

Bob Spink, Conservative to Ukip, 2008

When Douglas Carswell defected last month, poor Bob Spink must have felt like the least-remembered man in Britain after Twitter exploded with excitement about “Ukip's first MP.” Spink defected to Ukip in 2008—though the party at the time claimed it had sacked him. In stark contrast to the uber-democratic Carswell, who set a precedent followed by Reckless in calling a by-election and resigning, Spink remained in the Commons without seeking re-election. He has recently spoken of being intimidated by Tory colleagues, telling the Financial Times that they “resorted to public school bullying and banter” in an attempt to diminish his influence.