Penny Mordaunt has Irish Catholic roots, it has emerged, but her staunch support for Brexit makes her an outlier not just among many of those with Irish heritage but among her extended family. “She is the only member of the family – brothers, father, uncles, cousins and others – that supported Brexit,” her uncle Henry Mordaunt said as he revealed that the family’s Catholic ancestors fled England and moved to Ireland, possibly to escape religious persecution after Henry VIII’s Reformation. He said it was a “complete surprise” to see his niece emerge as a frontrunner to become the UK’s next prime minister, given she had a low public profile during Boris Johnson’s leadership. “I disagree with her politics, unfortunately, but I would be happy for her if she achieves her ambition,” he told the Irish Times. The MP’s paternal grandfather, Edward Mordaunt, was born to Irish parents in Canterbury, Kent. Her uncle said reports that her grandfather had supported the IRA during the 1922–23 Irish civil war were incorrect. “He refused to take part fighting fellow Irish men in a civil war when he was called up and so he was interned,” he said. His extensive research into the Mordaunt family history found that the Mordaunts were likely to have come to England as part of the Norman invasion in 1066. Some of them fled in the mid-1600s to Ireland. Records do not exist to confirm the reason why some of the family ended up in Ireland but Henry Mordaunt believes it was part of a “substantial movement of Catholic English emigrants to Ireland” in the 16th and 17th centuries as anti-Catholic laws were not enforced so heavily there. Mordaunt has not mentioned her Irish links during her campaign nor revealed her views on the Northern Ireland protocol bill tabled by her leadership rival Liz Truss last month. If it becomes law, it would result in Britain tearing up part of its deal with the EU and giving hard-Brexiters including David Frost, Steve Baker and Mark Francois the clean break they have wanted from Brussels. Each of the five candidates has sought to burnish their Brexit credentials and maintain support from the right of the party but only three – Mordaunt, Rishi Sunak and Kemi Badenoch – voted for Brexit. Only Truss, who voted remain but now presents herself as a hard-Brexiter, has mentioned the Northern Ireland protocol during the campaign. Advertising his Brexit purity, Sunak released a slick video over the weekend reminding party members he had “gone against the advice” of the then prime minister, David Cameron, and supported leave in the 2016 referendum campaign. Sources say Sunak has expressed reticence on the protocol bill in the past because of the risk of triggering a trade war with the EU. Last year Mordaunt spoke of the “unique disadvantages” Northern Ireland was suffering because of the protocol and the disruption to years of trade with Great Britain.