Julian was first elected as MP for Skipton and Ripon on 6 May 2010, with a majority of 9,950 votes.

After being re-elected in 2015, Julian joined the Government in the Whips Office, serving as Vice Chamberlain of HM Household from July 2016-June 2017.

In June 2017, Julian was re-elected as the Member of Parliament for Skipton and Ripon with a majority of 19,985. 

Julian was then promoted to Deputy Chief Whip, a position he held until being appointed Government Chief Whip in November 2017. Julian served in this role for just under 2 years.

Julian served as Secretary of State for Northern Ireland until February 2020, being appointed to the role in July 2019 by the new Prime Minister, Boris Johnson. 

Julian was re-elected with an increased majority of 23,694 in the 2019 General Election.