That brings back memories - the Troll Whillans was the first modern harness on the UK market and I bought one when they came out around 1970. I think I still have it in the shed.

Before that, we improvised a harness by wrapping tape around our waist and thighs. As befits the hippy '60s, this was called a Swami Belt.

The Whillans was tied on by passing the rope through two upper loops, tying it off with a bowline, and passing the active end of the rope through a crab clipped into the loop on the crotch strap.

EDIT: if anyone is rash enough to actually use this harness, please note that in the illustration the knot is on the wrong side of the crab - it should be on the live side, not the body side.

Note how the weight bearing crotch strap passes rather close to a delicate area of the male anatomy. This was in the era before sports climbing where leaders simply didn't fall, so I never tried it out in anger. But stories of dire consequences soon circulated and we quickly moved on to other designs.

As others have pointed out, quite apart from the terrible design webbing of this age will be lethally weakened, so for goodness sake don't use the thing. It quite literally belongs in a museum.