Stop whatever you're doing and watch these video clips.
After a brief holiday, it looks like they're back to filming the Robots of Sherwood episode, and if there's any doubt left as to who the fellow in green is supposed to be, here's an interesting take on the "Robin Hood meets Little John" part of the legend, with the 12th Doctor demonstrating some of that fighting prowess we haven't seen since the Pertwee era. (Not seen in the clip is a sequence filmed earlier of The Doctor and Clara standing in the middle of the log staring down into the river, so you can guess which one of the combatants ends up in the drink)
Here's Capaldi starting the duel:
And here's his stunt double finishing it (or at least blocking the finishing of it)
And here's one more from youtube user Michael Winks showing the TARDIS prop being set up (just in case you were worried they'd painted it pink or given it the wrong sized windows again)