Stewart had spent the 1940s running the Park Theatre Club in Glasgow's West End. When it folded, he turned his attention north. The Knockendarroch site was perfect: a wooded hillside above a Victorian tourist town that emptied out every summer. The problem was post-war Britain's planning bureaucracy, which would not grant building licences for what it considered a frivolous purpose. Stewart's response - to build a theatre that did not require a licence because it was technically not a building - was the kind of stubborn ingenuity that defined the project from the start. The Birmingham Arena Theatre had shown what was possible. The Walsall tent-makers knew their craft. Stewart bought, paid, and opened on 19 May 1951.

What made Pitlochry famous was not the tent but the rep. From the beginning, the theatre offered a true repertory season: six plays running in rotation through the summer, so a visitor staying three or four days could see a different production every night. The theatre claims, accurately, that no other theatre in the United Kingdom attempts this any more, and that the nearest comparable operation is in Canada. A 2018 season gave audiences Chicago, Tom Stoppard's Travesties, J. M. Barrie's Quality Street, Jim Cartwright's The Rise and Fall of Little Voice, Rodney Ackland's Before the Party, and Rona Munro's The Last Witch - musical, comedy of ideas, Edwardian comedy, working-class tragedy, lost classic, and contemporary Scottish drama, all in repertory.

Thirty summers of Perthshire weather are hard on a tent. By the late 1970s, the canvas had become semi-permanent through repeated patching, but everyone agreed something more durable was needed. A new building was commissioned at Port-na-craig, on the bank of the River Tummel below the original site. The architects Law and Dunbar-Nasmith delivered a low, glass-fronted structure with sweeping views across the river toward Ben Vrackie. It opened on 19 May 1981 - exactly thirty years after Stewart's first tent. A £25 million expansion that began in 2014 was delayed by the pandemic, but the theatre reopened in August 2022 with a refurbished foyer and a new 172-seat studio. The 2020 closures were turned into an opportunity to refurbish the outdoor amphitheatre and build a bandstand for summer performances.

In 2025, the theatre announced that the Scottish-American actor Alan Cumming - veteran of Cabaret, The Good Wife, and a Tony-winning career on both sides of the Atlantic - would become artistic director. For a regional theatre to land a name of that stature was extraordinary. For Pitlochry, which has spent seventy-five years insisting that ambitious theatre belongs in a Highland tourist town, it was the logical next chapter. The Leon Sinden Awards, named for an actor who spent eight seasons here between 1965 and 1994, still go each summer to performers in supporting roles, voted by the audience. The tent is long gone. The faith Tom Johnston spoke of is still building.