"Since 2023, I and a couple of other key members of the Film is Fabulous! team have been aware of a large collection of films, thousands of films, that have become vulnerable. That collection contains some very important material including a missing episode of Doctor Who."

I assume this refers to Network (now defunct UK home video company) founder Tim Beddows, who passed away unexpectedly in 2023. I remember reading an article about the drama that unfolded thereafter (sorry, no links), which mentioned him having a large, private collection of vintage material, and the first thing I thought is that he probably has a missing episode or two of Who.

Obviously the missing episode of The Web of Fear is out there somewhere [0], and I recall speculation, probably from the Roobarbs web board [1] that "a couple lost episodes of The Dalek Masterplan are in private hands".

[0] https://en.wikipedia.org/wiki/The_Web_of_Fear [1] https://www.zetaminor.com/roobarb/forum.php