Profile: Douglas Carswell MP
Douglas Carswell has made history by becoming UKIP's first elected MP, after winning the Clacton by-election he triggered after defecting from the Conservatives with a majority of 12,404.
So how did the 43-year-old reach this point in his political career?
A free thinker, who led the campaign to unseat Commons Speaker Michael Martin in the last Parliament, Mr Carswell has never hidden his disdain for the "job for life" culture among some MPs in safe seats and the "cosy cliques" that dominate decision-making in government.
Most newly-elected MPs put their head down and get on with the job of climbing Westminster's greasy pole.
But the Clacton MP, who entered the Commons in 2005, refused to play the game from the start, speaking openly of his "revulsion" at the system and how, frankly, he was embarrassed to be an MP.
In his book, The Plan, co-authored with Tory MEP Daniel Hannan, he set out 28 steps to "renew our broken democracy" and "get our supine, spineless Parliament off its knees".
He had high hopes that David Cameron, whom he backed in the 2005 Tory leadership contest, would push through some of their proposed reforms - such as open primaries, where all voters in a constituency get to choose party candidates, and giving voters the power to recall their MP if they are doing a bad job.
But in February this year he was, along with other maverick backbench Tories, bitterly disappointed to see plans for recall powers dropped by the coalition.
He told BBC News: "This government could have been different, but I think this marks the moment at which it becomes just another administration."
This - together with his belief that the Conservatives were not truly committed to changing Britain's relationship with the EU - undoubtedly fed into his decision to jump ship to UKIP.
Mr Carswell has long agitated for a referendum on whether Britain should remain in the EU - an institution he views as being profoundly undemocratic and lacking in accountability.
He is an ardent believer in the power of the internet to revolutionise the way we are governed - by smashing open closed institutions such as the EU and handing direct democratic control to the public. He set out some of these ideas in his 2012 book, The End of Politics and the Birth of iDemocracy.
In December 2009, he introduced a bill before the House of Commons requesting a public referendum on the UK's EU membership.
And in his first week after being re-elected at the 2010 general election, he revealed he intended to force a referendum on the Treaty of Lisbon.
Among his rebellions, Mr Carswell tabled an amendment expressing concern over the increase in the EU budget in October 2010.
Born in 1971, Mr Carswell spent his early years living in Uganda, where his parents worked as doctors in a local hospital.
He was educated at the University of East Anglia and King's College London, and worked in digital television, investment management and the Conservative Party policy unit - run by David Cameron - before becoming an MP.
He is married to Clementine and has a daughter. In his spare time, he has said he enjoys swimming, running, gardening as well as making quince jelly.
Mr Carswell reportedly owns a £655 love seat in deep moss brushed cotton while his father was the inspiration for James McAvoy's character in the Last King Of Scotland, the British doctor who went to work in Uganda and found himself working for Idi Amin.
Mr Carswell first stood for Parliament in 2001, taking on Tony Blair as the Tory candidate for Sedgefield. Despite apologising for coming second he still managed to cut Mr Blair's majority by more than 7,500 votes.
In 2005 he was elected as MP for Harwich, defeating Labour's candidate by just 920 votes. By 2010 he defeated the same opponent by 12,000 votes - although boundary changes had seen the seat renamed Clacton.
During that contest UKIP did not field a candidate, supporting what they saw as the re-election of a kindred spirit.
Mr Carswell went on to gain a reputation as an outspoken Tory moderniser, influencing initiatives such as David Cameron's Big Society and campaigning for the reform of parliamentary expenses following the 2009 scandal.
He once told the BBC he was attracted to politics because "our democracy is being undermined, with remote and unaccountable elites making the key decisions that affect our lives".
Adding to his other accolades, the MP revealed on Twitter in January that he had brought down a suspected shoplifter in his constituency.
"You probably don't want to hear this, but I'm your local MP," he reportedly told the individual.
Mr Carswell's bold announcement may not have been out of character, but he said the decision to leave the Conservative Party has given him sleepless nights.
He has vowed to fight on for "fundamental change in British politics" - something he now believes only UKIP can deliver.
In the by-election on 9 October, Mr Carswell won 60% of the total number of votes cast, and secured a majority of 12,404.
Addressing local voters after his victory, he said: "I resigned from parliament to face this election because I answer first, foremost and last to you. You are my boss. I will not let you down."
"To my new party I offer these thoughts: humility when we win, modesty when we are proved right. If we speak with passion, let it always be tempered by compassion."