The Apple TV+ streaming series is frequently dubbed the "anti-Bond" by critics. It stars Sir Gary Oldman as the crude, slovenly head of a team of disgraced MI5 agents who have botched their assignments and been banished to a dreary department known as "Slough House."

In a video posted on MI5’s official Instagram account, McCallum was asked: "What do you really think of your friends 'across the river' at MI6?" (The headquarters of the two agencies sit on opposite banks of the River Thames in London).

"You might say there's room in the world for both James Bond and Slow Horses," the counter-intelligence chief replied. "But personally, I'm probably in the Slow Horses camp."

"I suspect whoever asked the question was hoping for a tale of rivalry. But the truth is, the people at MI6 are our friends and colleagues," he added.

Slow Horses is based on the bestselling book series by Mick Herron and premiered in 2022. The show has been a massive hit; its sixth season is scheduled to release this September, with a seventh season expected in 2027.

Sir Gary Oldman remains the driving force of the series. His character, Jackson Lamb, is an unkempt, functional alcoholic, yet brilliant operative whose trademark is his distinctly ungentlemanly behavior.

In a 2024 BBC interview ahead of the Season 4 premiere, Oldman described the show's gritty atmosphere: "It's the underbelly of espionage. It's the kitchen-sink version of intelligence, if you like—espionage fueled by supermarket tea."