In 1969, Sir Ian McKellen and James Laurenson starred in a production of Christopher Marlowe’s classic Renaissance play Edward II as part of the Prospect Theatre Company. The production would lead to the first gay kiss to be shown on television in the U.K.

Edward II is one of the earliest English history plays. A contemporary and rival of William Shakespeare, Marlowe dramatized the ill-fated king’s reign and highlighted his relationship with one of his “favourites,” Piers Gaveston, an English nobleman who was rumoured to be his lover.

One of the first stops of the production starring McKellen and Laurenson took place at the Edinburgh International Festival in 1969. While homosexuality was recently decriminalized in England and Wales, it was still illegal in Scotland—and would continue to be until 1980.

The play was set to be performed in a theatre owned by the Church of Scotland, which drew the ire of a local councillor because of its gay themes. The performance was ultimately deemed “fit for consumption” by local police and the controversy even led to the show selling out during that run.

After touring much of the U.K., the production landed in London, where it would remain at the Piccadilly Theatre for three months in 1970. It’s during this time that the play was filmed for BBC Two. On Aug. 6, 1970, the filmed production—including McKellen and Laurenson’s kiss—aired on television, making history as the first gay kiss on British airwaves.

McKellen wouldn’t come out publicly until 1988. But after making history, McKellen mentored Daniel Evans, another gay actor who took on the iconic role in a Royal Shakespeare Company production last year.

“You don’t have to be gay to play Edward II,” he told The Times. “But it helps.”