The writers of Slow Horses appear to have hidden a tribute to Heath Ledger in the fifth season of the show.

Gary Oldman plays the lead character Jackson Lamb in the Apple TV spy comedy series, and also starred as Lt. Gordon in Christopher Nolan’s beloved 2008 film The Dark Knight, and in episode five of the new season of Slow Horses, the two streams appeared to cross.

In a scene in which he becomes frustrated with his colleague, Oldman’s character snaps, “When you talk, I wanna stick a pencil in my eye and headbutt the table!”

Fans have speculated that this could be a sly reference to a memorable scene in The Dark Knight in which Ledger’s Joker intimidates a group of organised criminals by asking, “How about a magic trick?” before slamming a pencil into the table. “I’m going to make the pencil disappear,” he adds.

As one of the mob confronts him, the Joker smashed his head eye-first through the pencil. “Ta-da!” he exclaims. “It’s gone.”

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Ledger passed away at the age of 28, before The Dark Knight was even released in 2008, and went on to pick up an Oscar for Best Supporting Actor for his iconic role in the film.

Many of Ledger’s co-stars have continued to express their sorrow at his loss in recent years, including Paul Bettany, who said last month that he continues to be unable to rewatch A Knight’s Tale because he misses his co-star so much.

Earlier this year, Michael Caine, who played the butler Alfred in The Dark Knight, said he was left “terrified” by Ledger’s performance. “The smeared makeup, the weird hair, the strange voice. It was chilling,” he wrote. “Absolutely floored me the first time I saw him in action – I was terrified”.

The Slow Horses season five final was on October 29, but it has already been commissioned for a sixth season.