They had an early start, with Dichen up at 3:30am. At that point, none of us knew where they'd turn up. Clues emerged: sightings of "BM" unit signs near the airport, and then a tip-off from the flying club next door.
A tantalising photo of the action was snapped by a bystander. Tom Price treated us to a pic of himself as Andy Davidson, revealing the day's most exciting news: PC Andy is now Sergeant Andy.
It seems today's scenes are from episode 2, directed by Billy Gierhart.
John Barrowman, playing Captain Jack on Welsh soil for the fist time in 2 years, seemed delighted that fans had turned out for the filming, despite the inaccessible location.
Let's hope that the next few days bring them back into Cardiff. I'm with Jack on this: "The 21st century's when it all changes, and I hate the commute."