You have to understand that I love these mystery movies from the 30's and 40's, hence the 8/10. It's fun to just suspend disbelief and watch the films for what they are. Get a bowl of popcorn then sit down in your comfy place and let your mind go back to a time before all of the special effects and CGI, before political correctness, and enjoy the show. There are terrific gems to be found in these old films. If you are like me then pick up the DVD; you won't be sorry. "Charlie Chan in London" is a good'un. The digital restorations are excellent. Same ol' cheezy sound and dialogue centric script but without the audio and visual noise. The shakiness of the original is gone as well.
Sure you can criticize some of the ham acting but I find the characters and the dialogue fascinating. Although IMHO Elsa Buchanan is wonderful as the distraught maid who is shocked by the evil oriental skulking about the place, others would likely be less kind.
E.E. Clive as the more than a little thick Detective Sergeant Thacker is perfect, especially his uncorrected references to Charlie as "Mr. Chang".
I didn't realize Ray Milland was in the movie till I heard his unmistakable voice. What a distance from portraying Luke Skywalker's father! While I'm on about it: the quality of the acting in "Charlie Chan in London" is not much different from "Star Wars Episode IV". ;->
The "Charlie Chan" character and its portrayal by non-Chinese actors has come under some heavy, and valid, criticism for stereotyping and for washing over issues of racism. However, I think that such criticism should be noted and should not prevent enjoyment of these wonderful films. We (audiences) are not stupid; we can see plenty of evidence of paternalism, sexism, and racism in these movies. Eh, so what? The story and the script are a product of the time and are a window into the past. Not into real life directly, but the film is enlightening with respect to what was acceptable. Eighty years from now, I'm sure many current films will be condemned for all sorts of things that we take for granted now. Food for thought.
For me, the controversy and obvious difference in cultural values from today just makes these films more interesting. Mr. Chan's quiet approach to life in general and to racism in particular speaks well of his character. We pay attention to what Chan says because he is always interesting and insightful. What may be interpreted as a stereotyped, obsequious and blandly inoffensive "chinaman", is really a thoughtful individual with obviously strong family values and who is so confident that he does not have to try to change all of the flaws in the world around him.
He just has to solve the mystery and go back to his family.
The animation is a bit like anime meets the old Spiderman but somehow it works. Sometimes simpler is better. My teenage son and daughter get a big laugh out of every episode and the Martin/Diana relationship is so much like my kids it is creepy! Martin is all teenage boy with girls on the mind and an overactive imagination (er.. think "sock gnomes" being responsible for missing socks). He jumps to conclusions based on limited knowledge and has an unshakable faith in his own opinions; he also has absolutely no clue about acceptable social interaction. He can be a total pain but when it counts he stands up for his step-sister and his friends. Diana is all about doing the right thing and making sure the rules are followed... but the teenage girl in her manages to get out anyways.
Martin and Diana often act like 2 year olds when fighting with each other, and to emphasize the point they get redrawn as immature kids. The effect can be hilarious and my kids love their childish arguments. I don't point out to them how much it matches reality around our place.
The comment someone made about Martin/Diana being incestuous is just totally out to lunch. There really is nothing offensive about this show. Just fun with slime, aliens, weird monsters attacking quiet rural towns, and cursed objects that are found by innocent people. No one is hurt in the end, and Martin usually saves the day despite being such a doofus. And sometimes his bizarre theories ARE correct.
Not sophisticated but provides surprisingly satisfactory entertainment.
BTW: Martin's closet contains several outfits that all look the same. He changes his clothes but not his look.