Quite frankly this is better than I'd thought. The sets, acting and production are all excellent. Though most of the plots are highly predictable.
Stuart Martin truly did the role of William Wellington justice without letting him become the stereotypical DI who drinks too much and the exploration into Victorian homophobia was very well handled.
Honestly, if I had to point out any problem with the show it would be Miss Scarlet herself. The fault doesn't lie with Kate Phillips, but rather the character. What is supposed to be an independent, ambitious, intelligent and capable woman has, sadly, soured into an arrogant and, at times, borderline cruel person who does her work not to help people or show a woman is capable of being a private detective, but rather prove her own superiority. And, when this is pointed out to her, she uses it as an excuse to belittle people. While these are meant to be key flaws of her personality to avoid us having a 2D character, it has instead consumed the character and left Miss Scarlet with no redeeming feature who is so unlikeable that it's hard to root for.
It's a shame because otherwise this is a reasonably decent show.