I kind of agree with @janetteb – this one seems like a story stretcher. Having set up that Devil’s End is genuinely dangerous, with a dead archaeologist and an Ice-Doctor, there’s then a lot of getting the gang together. Not to mention a certain amount of plot induced stupidity – I think I’d be happier with Mike Yates if there’d been mention of a platoon following by road.
Possibly they couldn’t afford more than a couple of UNIT extras in the episode. Between the helicopter shots, the three cameras on location so they could make the most of their time, and the exploding van, this episode felt surprisingly expensive.
Minor notes from the commentary. The director noted that he’d directed John Levene very badly when he was rescuing Miss Hawthorne; he goes immediately to the chest she’s tied up in. And this episode was recovered in black and white, then painstakingly re-colourised by a restoration team.