You can expect a bombardment of birthday celebrations this October when the National Theatre turns 50. But before London’s luvvies go wild, there’s another new-minted quinquagenarian closer to home worth championing: Edinburgh’s Traverse Theatre.

Yes, the heart and home of Scottish new writing is 50 years young – and boy, has it had a colourful half-century. What else would you expect from a theatre founded in a former brothel and doss-house just off the Lawnmarket? In 1962, 15 James Court was a temporary Fringe venue before a group of friends (led by actor John Malcolm), moved in the following January. Their intention was to keep the Fringe spirit of radicalism running all year round.

They certainly managed that. At only the second performance, actress Colette O’Neill was stabbed onstage because the company couldn’t afford a proper stage knife. The incident sent O’Neill off to hospital and the Traverse straight into the press. Controversy followed controversy: in 1965, there was a complaint in the House of Commons about obscenity but, undeterred, Gerald Scarfe produced six-foot genitalia costumes in 1967 for Ubu in Chains. And the following year, a student production, Mass in F, featured a topless woman recounting her sexual exploits

But to reduce the Traverse’s history to just its choicest anecdotes – the night, for example, when a radio mix-up resulted in the chatter of local cabbies broadcasting in lieu of the voice of God – would be to do it a major disservice. What began as a 60-seat theatre club, allowing it to evade the red pen of the Lord Chamberlain’s censorship, can today lay good claim to being one of the five most important new writing theatres in Britain. It’s even been described as a sort of unofficial national theatre of Scotland.

There are a number of factors behind this success. First, perhaps, there’s the turnover of leaders. In its first 25 years, the Traverse had ten different artistic directors, compared with two at the National over the same period. Each brought their own set of governing principles, righting what they saw as an imbalance of the previous order.

In 1964, Jim Haynes put the emphasis on new work, staging 31 world premieres in two years, while his successor Gordon McDougall pushed against programming for the sake of newness. Max Stafford-Clark programmed avant-garde experimentation, Michael Rudman sought to counter financial instability with populist dead certs and Mike Ockrent introduced an internationalist feeling. Then, in 1975, Chris Parr placed the emphasis squarely on Scottish writers. With all these shifts, today’s Traverse can draw on a rich and fluid tradition without betraying its core identity.

That fluidity has been aided and abetted by the nature of the theatre’s various stages. The first venue had two banks of seats either side of a 12’ by 9’ stage – a set-up actually known as transverse, but mistaken by those naming the Trav. The 1968 move to an old warehouse at 112 West Bow in the Grassmarket brought in a flexible stage, while since 1992 – when the new theatre became the first purpose-built new writing theatre in Europe – it has had an open end-on stage and, downstairs, a thrust stage studio. None of these are purpose-built for the social realism so dominant south of the border and the Traverse has been able to build on Scotland’s more radical, often folk-infused, theatrical tradition as a result: think Liz Lochhead and Tom McGrath or CP Taylor and Zinnie Harris.

That spirit was at the heart of the groundbreaking 1985 season. Under artistic director Jenny Killick, only 25 at the time, the theatre turned out eight in-house productions, all with vast scope and bold sensibilities. The plays included Peter Arnott’s White Rose, Chris Hannan’s Elizabeth Gordon Quinn and Losing Venice by Jo Clifford. Tilda Swinton and Ken Stott were amongst those performing. ‘It put Scotland on the map,’ Clifford told The List two years ago. ‘You can see the legacy of it today in the National Theatre of Scotland and the massive international success of Black Watch and now, when there is a hit, the structures are in place for it to go abroad and get the kind of exposure it needs to establish itself in the repertoire.’

You see its legacy, too, in the world-renowned playwrights to have come out of the Traverse in the last 20 years under artistic directors Ian Brown, Philip Howard and Dominic Hill: David Harrower (Knives in Hens), Gregory Burke (Black Watch), and David Greig (The Cosmonaut’s Last Message to the Woman He Once Loved in the Former Soviet Union).

There is, of course, the small matter of the Fringe itself. The Traverse is at its heart; its annual programme being the first point of call for serious festival-goers. The Traverse’s proximity to the flood of work on its doorstep each August has allowed it to cherry-pick some of the best emerging talent around: Scottish writer-performer Kieran Hurley and recent Olivier award nominee Caroline Horton being the latest examples. Nor is its programme confined to new writing. Belgian provocateurs Ontroerend Goed and American experimentalists The Team have both been Traverse mainstays in recent years.

That said, the Traverse can claim some of the most legendary plays to come out of the Fringe: Anthony Neilson’s haunting three-hander Penetrator landed in 1993, Tracy Letts’ Killer Joe came a year later, followed by Sarah Kane’s Crave in 1998. A very young Cillian Murphy starred in Disco Pigs which made Enda Walsh’s name and, more recently, Simon Stephens’ Pornography – fast becoming a modern classic – courted controversy in 2008 with its focus on the 7/7 bombings.

Such rich, fierce and exhilarating plays as these gave the Traverse its reputation; one that arguably played a part in the decision to have a roaming National Theatre of Scotland. With Orla O’Loughlin at the helm and a programme of 50 short plays to mark its half-century, the Traverse will doubtless produce many more.

Traverse Theatre celebrates its 50th birthday on Sun 9 Jun alongside the Critics’ Awards for Theatre in Scotland.

Traverse Festival programme 1978, featuring John Byrne's Slab Boys

John Byrne in The Traverse

Tilda Swinton in Peter Arnott's White Rose, 1985

Billy Connolly at The Traverse

Robert Carlyle in Dead Dad Dog, 1988

Animals, 1979

Robbie Coltrane in Slab Boys, 1978

Allen Ginsberg performing at The Traverse, mid-1960s