What you see on the flying suit leg patch is the standard aircrew survival knife, primarily for cutting parachute rigging lines but also anything else a knife is useful for, the handle also has a very useful notch in it perfect for opening beer bottles! The canopy on a Canberra is considerably thicker than a Vampire as it needs to support a larger area of pressure differential so a knife is totally out of the question. It's hard enough to break with an axe as it bounces off when you hit it so the trick is to use the escape axe at the edge of the canopy where it meets the fuselage metalwork. This cutting area is marked in black with a "chop here" placard.