What does HM stand for?

Robert Llewellyn probes the hidden machines and structures most of us take for granted.

On the third morning, a jeep carrying Pyle and three officers came under fire from a hidden machine gun.

Complete with ejector seat, hidden machine gun and rear window bullet-proof shield, it became a classic that sold millions.

The fact is that what makes this game a game unlike any we have seen before is not because it is, mirabile dictu, a game of computer chess; what transforms this game into a unique event is what goes unseen - Deep Blue's "brute force search" (the juggernaut of combinations hurtled around in the depths of a hidden machine accessed by a thin, unassuming monitor) and the intellectuality of Kasparov.

It was Hollis who prevented the annihilation of these vanguard troops, when they by-passed a cunningly hidden machine gun pill box.