The central fact that the whole thing is designed to frame and throw into sharp relief is that, shortly after the event, a representative of Smiths asserted that Smiths were the sole watch on the summit of Everest in 1953 and a representative of Rolex conceded that this was the case. Both representatives had access to all the information they needed to be sure and if their statements are not an example of a historical fact then nothing is.
Sometimes we do have to accept that things can’t be known, but this isn’t one of them.
If you look at Norgay’s wrist and see a gold Datejust then you really should have gone to specsavers. If you see two watches on Hillary’s wrist in the seconds before the final climb, or at any other time, then you’ll need to point it out because in literally hundreds of hours of looking at pictures, including literally every one held at the Royal Geographical Society collection, I’ve never seen it.
All the evidence in the case of Richard III is circumstantial. If we had written reports from, say, John Argentine accusing Richard of the murder and a written confession from Richard conceding he did murder them, all backed by pictures of the preparations and aftermath of the murder then we’d have an equivalent situation.