They did a couple of revisits on that one... Adam's big array was far too bendy.
It's certainly possible to set fire to things with mirrors. Whether it's possible that Archimedes actually did it during the siege of Syracuse is another question... And whether he actually
did do it is a third.
What really annoyed me on that one was that they concluded, straight off the bat, that it's impossible to accurately aim a mirror by hand over a distance of more than a few feet. I'm sure this came as a big shock to anybody who's competent in the use of hand signal mirrors...
I presume that the show that started this thread off was Adam Hart-Davis' "What The Ancients Did For Us", which also annoys me because he states that Archimedes
did do it, despite the total lack of any contemporary accounts and the highly questionable nature of the claim.
Yes, I am a curmudgeon.