Filming has begun on episode 9 of the latest series of Doctor Who, and we have our first batch of set pics, courtesy of Twitter users colseywolsey and Leanne Roberts, which seem to indicate a particularly creepy new form of alien invasion.

To backtrack a bit, we heard a number of potentially leaked working episode titles a few months ago, including several for stories that hadn't even begun filming. Oddly enough, every single one of them appears to have been true.

For instance, the one for this episode was Flatline, which makes sense if someone or something is running around turning people into 2-dimensional artwork.

From set reports, we now know this episode is set in Bristol, and features quite a bit of urban graffiti-themed set-dressing. In addition to the strange backwards facing people there's also a large mural depicting a potential 2-dimensional alien invasion (or exodus... or maybe the 2-D aliens are just looking for friends, and can't understand why humans don't like to be flattened) and a missing persons shrine.

It's also possible this may be a Doctor-lite episode, as filming today involved Clara traveling alone, but wielding the sonic screwdriver, investigating strange goings on inside a tunnel, while guest stars Christopher Fairbank and Joivan Wade's characters are stuck on community service clean-up detail. (Here's a short video from this morning showing Jovian's character searching for someone.)

One of the other episode titles we heard was for episode 8, Mummy on the Orient Express. (This is the one written by comedian Jamie Mathieson, guest starring Frank Skinner, and featuring a cameo from singer-songwriter Foxes.) After Dinosaurs on a Spaceship and The Angels Take Manhattan, I'm no longer willing to dismiss any episode title as too stupid or cornball to be true, and sandwiched in between everything else was this small bit of location shooting last week involving Clara sporting a very 1920's look, and what might have been some second unit stuff at the Hood Road train station. Plus Moffat did tease that this episode would involve "the Doctor catching up on his phone calls," which could easily be a reference to the call the 11th Doctor receives at the end of The Big Bang.

Finally, here are a couple of nice closeups of the spacesuits worn by Hermione Norris and Ellis George in episode 7, rumored to be titled Kill the Moon, which may or may not be a sequel to Planet of Fire, but certainly involved some location filming around the volcanic island of Lanzarote. (Note the vaguely NASA-ish logo on Hermione's suit)