Wait, I just realized something about "The Power of Three"
It was all a big elaborate tribute to the Third Doctor!
A Lethbridge-Stewart working for said UNIT.
The Doctor stuck on Earth with his companions.
Seemingly mundane inanimate objects – OF DOOM!
Reversing the polarity. (What the Doctor essentially did to the cubes.)
It all just adds up…
THE POWER OF THREE. As in THE POWER OF THE THIRD DOCTOR, JON PERTWEE.
I see what you did there Chibnall.