I don't normally critique individual mid-series episodes of Dr Who but I absolutely loved this episode. I've seen almost every TV and cinematic representation of Robin Hood going back to Errol Flynn and this adventure paid due homage to all that history, condensing most of Hood's best-known stories into its 50 minute time-frame (the "Little John"-type encounter on the log over the river, the archery contest set up to trap Robin by the Sheriff of Nottingham and even climaxing in a sword-fight between them, which if not exactly up there in the Flynn/Rathbone class, still paid its due respects).
Underlying the story were subtle questions about the need for heroes and the power of legends, with the Doctor denying the efficacy of both until he realises by the end that the same fate awaits the remembrance of his own exploits in the future. Sensing a rival for Clara's attention (affection?) in Robin, whose fictional dreamboat he's always been, the Doctor is immediately querulous and doubting of his Lincoln Green attired rival. Several quick-fire exchanges take place between them with Clara usually having the last word until they both man-up to take on the nefarious Sheriff and his robotic henchmen.
Cleverly, the plot doesn't allow the inevitable alien-presence to overpower the story and there's another cryptic reference to the promised land to hold the viewer's attention until the series closer. Capaldi is now completely in character and relishing his role, Coleman, her puppy love now replaced by qualified respect is very good too. Perhaps it would have been nice to see more of Robin's Merry Men (Little John, for one, barely gets a line) but this overdue combination of the Doctor and Robin Hood already has the look of the series high-spot.