In his current role, Mascall is the controller of the Government’s communications 'grid', setting the direction for the timing of all government activity, policy announcements and media strategy.
He was previously special adviser to then defence secretary Michael Fallon, and before that to then transport secretary Patrick McLoughlin.
Mascall, who was also deputy director of comms for the Conservative Party in the run up to and during the 2015 general election campaign, is set to join Headland in September.
He is the latest high-profile hire at the agency, following former Finsbury UK CEO Mike Smith and Ed Young, an ex-Tesco corporate comms chief and a former speechwriter for David Cameron, whose appointments were announced in April.
The City of London-based agency has also hired Gabriel Huntley, currently head of communications at the University Alliance and previously a political adviser to Chuka Umunna, as an associate director; and Harriet Beaumont, of comms agency Lexington, as an account director.
The appointments follow a period of strong growth for the agency, whose revenue rose 51 per cent in 2017 to reach £7.1m, according to PRWeek’s UK Top 150 Consultancies table. It followed client wins including PepsiCo, Three UK, and fashion brand Mulberry.
CEO Chris Salt said: "Ben, Gabriel and Hattie are fantastic additions to the team, bringing unique experience from across politics, government and the media to Headland’s clients. We’re excited to offer their insight and thinking at such a critical time for the UK."
Mascall said: "Headland is a fresh, bold company, set up perfectly for the kinds of communications challenges that organisations face as we head towards the 2020s. Like the many new clients that are turning to it for ideas and solutions, that’s why I’m joining."