After finishing Gore High School, Barclay went to Victoria University in Wellington to study for a Bachelor of Commerce, majoring in commercial law.
He got a internship with English after emailing him out of the blue, and later worked for then-Prime Minister John Key and Cabinet ministers Gerry Brownlee and Hekia Parata.
He left those roles for a job with the public relations firm SweeneyVesty before becoming corporate affairs manager for the cigarette company Philip Morris.
He told Fairfax after his election: "The company's a legal company selling a legal product. No smoker, or non-smoker in the country can say they're not aware of the consequences of smoking and that they didn't know where to go to seek assistance if they want to quit."
Entering Parliament, Barclay took on the role of deputy chair of the Law and Order Select Committee.
His chances of retaining his safe seat were reduced after it emerged that police were investigating claims he had recorded staff working in his office. Several long-serving staff members for Barclay's predecessor English also resigned in quick succession.
But he survived a potential deselection late last year and was reconfirmed as National's Southland nomination. A number of sitting MPs rallied behind him during the nomination process, including Judith Collins.
Barclay suggested that he had been vindicated by his victory, saying it was robust and transparent, and that he had won "quite convincingly".