So, fight scenes on Doctor Who rarely go well. That mostly works since most incarnations of the Doctor, the Third Doctor being a big exception, paint the Doctor less as a man of action and more of a man of wits. He doesn’t really go for violence. When the show does, it often doesn’t look particularly good.
But sometimes, they seem to pull something off.
What I mean here is that there’s actually a somewhat impressive sword fight in this episode. Grendel kidnapped Romana (again) and basically threatened her into marrying Prince Reynart under the guise she is really her lookalike Princess Strella. The real Strella is still refusing to marry Grendel, but somehow forcing Romana to marry Reynart will fix that while Romana claims to be Strella.
I’m sure there was an explanation for that, but I probably missed it.
While this is going on, the Doctor and Reynart’s loyal retainers device a plan. If someone can get Grendel’s gate open from the inside, the others can storm the gates and save the day. Since this is the Doctor’s show, he and K9 get to take a small boat under the castle, through some tunnels, and then into the building. K9 stays with the boat because clearly leaving the dog with the laser nose behind is always a good idea, and the Doctor goes in, stopping the wedding just in time.
Grendel, then, challenges the Doctor to a sword fight with their electric swords. Grendel is, we’re told, the best swordsman on Tara. The Doctor is…well, he figures he can pick it up along the way.
Maybe he was remembering his previous incarnation, but he actually does pick it up along the way, even blocking an attack when he wasn’t looking, and without having to move his giant scarf around too much. The fight goes down a tunnel, into the dark, and while Romana saves Strella and Reynart opens the gates, the Doctor prevails, causing Grendel to shout a quick “NEXT TIME!” which never comes before jumping off a balcony to swim away in the moat below.
So, time to head back to the TARDIS I suppose. The Doctor did stop to scoop up that piece of the Key of Time on his way to the wedding. They just need to fish K9 out of that boat, which is about all the Doctor caught on this fishing trip.