The assistant director set the explosions off for what he thought was the take, but was actually the final run-through. Mankiewicz tells the story of the fellow abjectly apologizing over and over to Hamilton, who tells him to shut up, and proceeds to direct with only half of the planned number of cameras running. Mankiewicz said it was the greatest job of directing under pressure he ever witnessed.
This anti-spectacle climax fits with the entire “anti-” aesthetic of the film: isn’t this only Bond movie where the weapon/threat is left intact, just waiting in space for someone to re-take control.
1971 was a good year for "anti-"aesthetic cinema: A CLOCKWORK ORANGE; THE FRENCH CONNECTION; MCCABE AND MRS. MILLER; THE ANDERSON TAPES; TWO-LANE BLACKTOP