Continuity mistake: The windows in the sedan with the British spy go from clear to black from the time it stops in the junk yard until it is put in the crusher.
Visible crew/equipment: When the "blind" spy is talking with the British agent, the lighting rigs are reflected in his shades a few times.
Chosen answer: The actors were weighted down with lead plates. Oxygen tanks were kept just out of picture, and the actors used them to breathe between takes. The takes were short enough to allow the actors to hold their breath through them. The short takes were then cut together to appear as one long fight. Sound effects were added post-production.