'Slow Horses' has been a hit with fans and critics, but it didn't come cheap.AppleIn recent years it has become common for Hollywood studios to make a point about how they have slashed their streaming budgets after subscriber numbers fell following the end of the pandemic. It seems that some shows have dodged that bullet.Hit Apple TV+ spy series Slow Horses is a case in point. Recently released filings reveal that the production company behind the British thriller spent a record $101.2 million (£73.8 million) during the year to June 30, 2025 when its upcoming sixth season was filmed. It brings the total spent on the series so far to a staggering $455.4 million (£350.5 million) with at least one more season still to come.Slow Horses follows a group of failed MI5 agents played by an all-star cast including Kristin Scott Thomas, Gary Oldman, Jonathan Pryce and Hugo Weaving. Its title refers to the fictional central London base where washed up veteran spies are sent to endure a life of drudgery. It doesn't pan out like that of course as the rejects get dragged into crucial cases complete with all of the intrigue and danger found in other spy sagas.The first season debuted in April 2022 and became an overnight success with critics and audiences alike. The former rated it 95% on review aggregator Rotten Tomatoes while the latter gave it 89%. Both praised the show for being the antithesis of James Bond thanks to a distinct lack of flair and flamboyance. Indeed, Oldman's character became so famous for his dishevelled appearance that when the British actor picked up his knighthood, Prince William told him that every time he sees him in the show he wants to give him "a good wash".Gary Oldman has been praised for his performance in 'Slow Horses'AppleMORE FOR YOUThis gritty realism is reflected in the Rotten Tomatoes' critics' consensus for the first season which says that "Slow Horses refreshes the espionage genre by letting its band of snoops be bumbling, with Gary Oldman giving a masterclass in frumpy authority."Its storylines keep audiences on the edge of their seats and this set the scene for a series of shows. There is no shortage of source material as Slow Horses is based on a collection of 14 books written by British author Mick Herron.Against the odds, the second season improved on the first and critics gave it a 100% rating when it debuted in December 2022. By then, Apple knew it had a hot property on its hands and renewed it for two more seasons. The fourth repeated the trick as critics again rated it 100% making a fifth season inevitable. It came to a crescendo in October last year with an episode which earned yet another perfect score.New York Magazine described the episode as "supremely satisfying" while the Daily Telegraph praised it for being "very funny, impeccably acted". Metro added that it "balances humour, action and great character work."Ahead of the debut of the fifth series, Apple renewed Slow Horses for a sixth and seventh season with the former set to debut this fall. In an attempt to keep audiences guessing about the plot, it will be the first season which is based on two of Herron's books rather than one as usual. There is a lot on the line.No expense is spared on Slow Horses. From its A List cast to its title track which is performed by Rolling Stones frontman Mick Jagger, who wrote the song with composer Daniel Pemberton, it doesn't come cheap.The cost of making streaming shows in the United States is usually a closely-guarded secret as studios typically combine all their productions in their overall expenses and don't itemize how much was spent on each one. It is a different story for shows like Slow Horses which are made in the United Kingdom.U.K. production companies have to file publicly-available financial statements which show everything from their headcount and salaries to their total cost. There is good reason why studios are prepared to put up with this level of transparency.The production companies benefit from the U.K. government's Audio-Visual Expenditure Credit (AVEC) which gives them a cash reimbursement of up to 25.5% of the money they spend in the country.'Slow Horses' is filmed in the U.K.AppleIn order to qualify for the reimbursement, at least 10% of the core costs of the production need to relate to activities in the U.K. Each season of Slow Horses passed this with flying colors as they were filmed on location across London at historic sites such as Regent's Park and Greenwich's Old Naval College.U.K. production companies usually have code names so that they don’t raise attention with fans when filing permits to shoot on location. The company behind Slow Horses is named Jackson River Films after two of the spooks – Oldman's Jackson Lamb and fellow actor Jack Lowden's River Cartwright.As with all U.K. companies, the financial statements are filed long after the period they relate to which is why the latest set for Jackson River Films cover the year to June 30, 2025. All of the filming for the sixth series took place during that period along with some for the previous season. The $101.2 million cost incurred in the 2025 financial year was higher in dollars than the spending on series five in 2024 (see box) and although more was spent in 2021, that resulted from the filming of two seasons so it is not a like-for-like comparison.The cost of making 'Slow Horses'Caroline ReidPost-production of the sixth series also got underway in 2025 and at the same time season five was wrapping up ahead of its debut in September last year. Post-production isn't believed to represent the majority of the spending as Slow Horses isn't filled with visual effects which typically account for a great deal of the cost. One of the biggest single expenses was the $11.3 million (£8.2 million) spent on the crew which came to a monthly average of 115 people. That doesn't even include freelancers, contractors and temporary staff as they aren't listed as employees on the books of British companies even though they often represent the majority of the workers on a film shoot.Jackson River Films got a helping hand from the U.K. government as it banked $18.5 million (£13.5 million) from the AVEC in the 2025 financial year bringing its net spending to $82.7 million. This windfall had a magic touch as the filings reveal that "the estimated total cost of the programme was in line with the budget".Since production began on the first season of Slow Horses, the company has been paid a total of $82.8 million (£63.8 million) by the U.K. government bringing its net spending down to $372.6 million. It wasn't just a welcome relief for the company's French owner, the media conglomerate Mediawan, but also for Apple which funds the production of Slow Horses as it distributes the show.This is explained in the financial statements which state that in return for the funding, "Apple Video Programming LLC holds a fixed and floating charge over the company which entitles it to the rights, title and interest in the entire copyright and all other rights in relation to the production." It is money well spent.Slow Horses is one of Apple's most successful shows as it has won multiple Primetime Emmys and BAFTA Television Craft Awards. Even though it has been running for five seasons it has managed to maintain momentum with audiences thanks to a clever trick up its sleeve. The seasons are generally filmed back-to-back in pairs, long before either is broadcast, enabling the earlier series to carry a trailer for the next instalment straight after the finale.The stinger for season six showed that the spy team will be on the run after a leak leaves them vulnerable. It also revealed that Hugo Weaving will return as River Cartwright's father Frank Harkness, a cold-blooded CIA assassin who was last seen in season four when he escaped accountability for his crimes. It doesn't stop there.Apple has already announced that season seven will be based on Herron's 2022 book Bad Actors as it will see Lamb and his team attempt to "find and neutralize a mole at the heart of British government." Given how crucial the U.K. authorities have been to the success of the show in real life it couldn't be much more ironic.Additional reporting by Chris Sylt