I saw the Industrial Revelations programs first, THEN saw Mark Williams in the Harry Potter films.
After seeing Mark in Industrial Revelations I sent an email to the program producers giving very positive feedback about how the presenter of those programs knew his stuff - he came across as being a learned expert, so good was the presentation.
When I eventually got to see him in Harry Potter I thought back on my earlier comments and felt slightly embarrassed. I had no idea he was actually a professional actor and not a humble program presenter. However I wouldn't want to withdraw my early comments, Mark presents these programs in a wholly engaging way and whilst he might not be as sharp suited and clean cut as some other presenters his style is a welcome change.
Good on you Mark, keep up the good work.