Slow Horses is an Emmy-nominated funny espionage drama that follows a team of British intelligence agents who serve in a dumping ground department of MI5 due to their career-ending mistakes, nicknamed Slow Horses (from Slough House). The team is led by their brilliant but cantankerous and notorious Jackson Lamb (Academy Award winner Gary Oldman). In Season 4, the team navigate the espionage world’s smoke and mirrors to defend River Cartwright’s (Jack Lowden) father from sinister forces.
Season 4 of Slow Horses premiered on September 4, 2024 on Apple TV+. It is also subtitled “Spook Street” after the fourth book of the same name. Union VFX handled the majority of the visual effects, and the VFX supervisor was Tim Barter (Poor Things).
In the new season, the key VFX sequences beyond clean-up work and stunt work included the London explosion, the Paris château fire, the explosion in the canal, and the destruction of the West Acres shopping mall. Union VFX had done some work on season 3, and they were happy to take an even more prominent role in the new season, including on set supervision. In season 4, they had approximately 190 shots and 11 assets. For season 3, they worked on approximately 200 shots and 20 assets and were the lead VFX house.
Union VFX is an independent, BAFTA-winning, visual effects studio founded in 2008, based in Soho, with a sister company in Montréal. Union has established an strong reputation for seamless invisible effects on a wide range of projects building strong creative relationships with really interesting directors including Danny Boyle, Susanne Bier, Martin McDonagh, Marjane Satrapi, Sam Mendes, Fernando Meirelles & Yorgos Lanthimos.
The Union VFX team used a mixture of practical effects, digital compositing, and digital doubles/face replacement to achieve the desired VFX for the show. Interestingly, at one point, a hand grenade had to be tossed in a canal after it was placed in River’s hoodie. Not only was the water added digitally for the normal VFX reasons that one might imagine, – such as an explosion going off near the hero actors, but also water in the canal isn’t actually fit to be splashed on anyone, it just isn’t clean water, so the team did the water explosion fully digitally. Simiarly, the shopping mall at Westacres, which was meant to have 214 retail stores, 32 restaurants and 8 cinema screens was not actually blown up, but in fact the location wasn’t even in London and the background was all done with digital matte paintings to look like a real ‘Westfield Shopping Centre’ – hence the fictional equivalent’s similar name.
After the suicide bomb goes off at the Westacres shopping mall in London, carried out by Robert Winters. After Winters publishes a video confessing to the attack, a police force breaks into his flat, but three of the MI5 ‘dogs’ are killed by a booby trap. This explosion was genuinely shot in a backlot, and then integrating that into the plate photography of a block of flats.
The Park which is the hub of the MI5 operations has been seen before since season one but each season it is slightly different causing Tim Barter to analyse all the previous seasons work to try and build a conceptual model of what The Park building would actually look like, so that they could have continuity in season four with various interior, exterior and complex car park shots.
“In season four there was a requirement to do probably one night and five daytime aerial views of it from different angles,” explains Tim Barter. “We got to create a whole sections of the Park that have never been created before, so I was there going through the previous seasons, looking at all the peripheral live action shots that were all shot in very different actual locations. It’s like, – there is this section where River comes out of the underground car park, and then he gets into this little door over here, which then goes through here on the side of this. And all the time, I’m trying to retroactively creating that architecture (digital) of the Park, to be faithful to the previous seasons.”
After the Harkness breaks into Molly’s apartment and forces her to give him her security credentials, he tracks the River’s convoy of Dogs and sends the assassin Patrice to intercept. After slamming a dump truck into the convoy, Patrice kills four Dogs and kidnaps River. This extensive sequence was shot in London at night in the financial district, but that part of London is still an area where a lot of people live. “So there is no opportunity to have the sound of guns or blank muzzle flashes,” Tim explains. “It was all added in post. The dump truck that smashes into the SUV was also not able to be done in London.” It was filmed at a separate location and then the aftermath was recreated by the art department in the real financial district for filming. “The dump truck actually ramming the car was shot with green screens and black screens and lots of camera footage. We actually used much less than we shot, but we did use the footage to make up a series of plates so we could composite it successfully over a digital background.”
For the scene where Jackson Lamb hits the assassin with a taxi they started with an interior garage as a clean plate and then had a statement on wires tumbling over it various angles and then married this together. “Actually we ended up with marrying three live action plates. We had the garage, the green screen plate of the stunt actor, but then we also got clean plates of the garage interior as we were removing and replacing certain things in the garage,” Tim comments. “We also had to do some instances of face replacement for that.”
Another instance of face replacement was the half brother of River who gets killed at the beginning of the series in River’s father’s bathroom. Originally, this was a dummy in the bathtub but it looked a bit too obvious that it was fake, so an actor was cast and then the team re-projected the actor’s face onto the dummy in Nuke. Of course, there was also a lot of blood and gore in the final shot.
The film was shot at 4K resolution with exception of some drone footage which had to be stabilised and used for visual effects work so some instances the drone footage was 6K. This allowed the extra room to tighten up the shots, stabilise and match to any practical SFX or explosions.