And in the case of Yorkshire MEP Amjad Bashir, the referendum on Britain’’s membership of the European Union pitched him not only against the leader of his own party, but the man who had welcomed him into the Conservative fold just 18 months earlier.
As the first salvos were fired in the 2015 General Election campaign, Mr Cameron was pictured welcoming Mr Bashir as he defected from the UK Independence Party,
Mr Cameron described Mr Bashir’s personal story - arriving in the UK at the age of eight and going on to succeed in business - as “inspiring”.
But this year Mr Bashir was campaigning for Vote Leave as the then prime minister tried to persuade the country to remain in the EU.
Mr Bashir said he discussed his position with Mr Cameron before the referendum who “respected” his view.
He waited for Mr Cameron to conclude his deal with EU leaders before declaring his support for the Leave campaign.
Mr Bashir argues Mr Cameron’s EU colleagues did not take the possibility of Britain leaving seriously enough.
“I felt the Prime Minister, despite his best endeavours, had not been helped by his opposite numbers so he hadn’t been able to get the deal necessary for our people to buy and that’s why the vote was lost.”
The loss of the referendum led to the end of Mr Cameron’s premiership and Mr Bashir admits being disappointed at that outcome for a man who he credits for delivering the Conservatives their first majority government in almost 20 years.
“David Cameron and his team had done an excellent job in rescuing the country from the precipice. The Labour Party had left the country in dire straits.
“They rescued the economy and the people realised this which is why whereas in 2010 we formed the coalition government in 2015 with a majority we were able to govern by ourselves.
“It was sad to see him leave, I understand his reasons for leaving but I think he and his team did a very good job for the country.
“Theresa May can put her own mark on the premiership and she’s very sensibly said she wants the party to appeal to everybody rather than just a privileged few.
“This has special resonance for me as a northerner from a working class background. In the North we have post-industrial deprivation that we need to tackle, we need to give people in Yorkshire more opportunities and I think she’s going to be a great prime minister for us.”
The coming year promises to be no less significant as the UK begins formal talks with Brussels over the shape of relations post-Brexit.
The negotiations look set to focus on the extent Britain can continue to trade freely with EU nations while exerting more control its borders.
EU officials have been quick to assert that access to the European single market is indivisable from accepting freedom of movement.
“I think that we should have the maximum access to the European market for goods and services and I think that can be done whilst respecting the people’s wishes to control immigration, to control our borders, to have control of our money, our sovereignty, our laws.
“I think those are the broad parameters of the deal our prime minister will be negotiating. I don’t have any worries.”
Mr Bashir said Mrs May was respected in Brussels.
He continued: “I think a lot of posturing has been done, a lot of chest-beating, a lot of warnings that we are going to do this or that. I respectfully say to the Prime Minister and her team, don’t be in any way cowed by these people they are just trying to put pressure on.
“They are not going to get away with it, we are going to get a good deal for us and the rest of the EU.”
Beyond the talks with Brussels, six months on Mr Bashir remains convinced the bright future outside the EU promised by Vote Leave will be delivered.
“I am convinced that we have made the right decision. Nothing I have seen in Europe since June 23 has told me we’ve made a mistake.
“The world is our oyster. With the Foreign Affairs Committee I’ve been to Bahrain, I’ve been to Taiwan and these countries cannot wait to do trade deals with us.
“Next year I’ll be having a digital economy conference in London. We have a thriving digital economy, only second to the United States.
“We will be able to do trade deals that much quicker having left the EU and that will bring about huge chances to create jobs and if people are gainfully employed they can determine a better future for themselves.”