The Hidden Blade Assassin's Creed in Depth

A Carriage Strike from the highest tower in the game as suggested by DAZ. James Brudenell was the natural choice of target since he's in the adjacent Parliament building. However, it's difficult to get Brudenell into position for a Carriage Strike because he doesn't stand still.

Kill the Policemen in the garden

The main reason I do this is because policemen will kill Brudenell if they witness him in Open Conflict. Another reason is to clear a path to kidnap Brudenell and walk him over to Big Ben. I also clear one of the front gates in order to remove a carriage later. You don't have to kill all the policemen. Just the ones that may interfere.

Aggravate the Earl

The goal here is to make Brudenell run but then lose track of him. If you lose him inside the building, there's a game mechanic that moves him into the front hallway surrounded by four new Templars. From there he's more manageable to kidnap. You just have to locate him again.

Note that I use an undocumented Entry Point. Each of the three eastern courtyards has one door with a lock that may be picked. From there it's a short distance to Brudenell's office. If you use Eagle Vision and time it right, you can pick the lock and enter the hallway with stealth.

Instead, I intentionally enter Open Conflict in the first hallway. Sometimes this causes Brudenell to immediately flee, even though you haven't approached his door yet. It has happened to me many times but not while recording this video. I haven't characterized exactly what conditions cause him to flee early. So I had to go manually open his door. His bodyguards drop a smoke bomb and I go out the same way I came in.