'I was on the set of Slow Horses season five - one strange decision left me baffled'

The AppleTV sensation Slow Horses has returned to screens for a fifth season of the spy drama, which is fronted by Oscar-winner Gary Oldman. Oldman portrays the vulgar yet brilliant Jackson Lamb, the head of Slough House. Season five, which is out today (Wednesday, September 24), centres around a string of terrorist attacks, including a mass shooting. "Everyone is suspicious when resident tech nerd Roddy Ho (played by Christopher Chung) has a glamorous new girlfriend, but when a series of increasingly bizarre events occur across the city, it falls to the Slow Horses to work out how everything is connected," the official synopsis reads. "After all, Jackson Lamb (Gary Oldman) knows that in the world of espionage, 'London Rules' should always apply."

Now, I accidentally end up on the set for season five of Slow Horses, which was partly filmed in Harkstead, Suffolk. It's a historic village situated on the scenic River Stour, which looks over to the riverside town of Manningtree, in Essex. A couple of things really surprised me when I stumbled upon the set.

While walking along the eroded shoreline on a sunny weekend morning with the dog, I was confused to hear gunshots and see clouds of smoke coming from the end of the beach. As I continued walking towards the noise, it was clear I was on a film set, but it was difficult to work out what was being filmed and why.

I couldn't resist speaking to a crew member as I asked for directions, and she revealed the latest series of Slow Horses was being filmed.

While I couldn't get any closer, as I didn't want my dog to ruin any takes or start barking amongst all of the excitement, I walked up a huge hill into the village and was astonished by just how many props and crew lorries were parked on a nearby field.

There were dozens of trailers-an unbelievable number for an AppleTV show-and all of them parked in the middle of a field in the quietest location. Somehow, they managed to evade much public attention, as only the odd passerby or dogwalker appeared near the set.

What else surprised me was the amount of fake crops used for filming the sequence on the shoreline. A massive field next to the water was filled with artificial crops and camouflaged netting to "set the scene" for as far as the eye could see.

I'm surprised the set designers and crew took the time to make and lay out all of these artificial plants, and they were not added as part of the show's CGI.

What it did teach me was how important attention to detail is for the makers of Slow Horses - who clearly want every scene to look realistic and authentic.

While I can't reveal what the gunshots were about, the series can now be streamed on AppleTV along with the four other seasons of Slow Horses.