Space Digital is a visual effects production house that began work on Doctor Who with The Doctor, the Widow and the Wardrobe. As their website proudly proclaims, they completed 39 shots for the story, most of which seemed to be effects that improved the ambience of the scenes, but were not themselves the main VFX for the scenes.
The first story on which they were credited as the main VFX house was A Town Called Mercy. With that story, they became only the second entity to be so credited on a BBC Wales-produced episode of Doctor Who.
The stories on which they're provided VFX include: