Well, unfortunately I have to say that was my least favourite Sherlock episode to date.
I enjoyed the fact the the first episode was more character focused given the circumstances but I was hoping this episode would get back to the crime solving which it didn't really until the last half hour. And in comparison to last week which felt very dense and crammed with good moments, at times this one felt very slow, the stag night scene in particular seemed to drag on too long. I think it was all the jumping around in time which made the episode feel like it wasn't going anywhere.
Didn't help that I guessed the photographer would be the murderer after about 10 minutes. I noticed when rewatching a study in pink this week how prominently taxis are featured in the beginning, which is what had made the killer pretty easy to guess on my first watch. With this in mind on picked up from the long shot in the underground last week that it was somehow going to be a key part of the episode so I was really kicking myself when the reveal came that I hand't figured out the spies message.
This week however the foreshadowing was not lost on me and I picked up almost instantly from intercutting of photos and focus on people having pictures taken that the photographer was going to bad guy. So basically I hope they are more subtle in future with their clues because their techniques have become predictable.