Saving him will get you Free the station chief - Complete. Get the schedule, but kill all the enemies here, as some are beating up the chief. My next suggestion, is to find the Conductor. Now with this mission, you are generally free to do what you want. If you would prefer to use a video, here is one for this memory: Memory 3 - Survival of the Fittestġ00% Sync Requirements - Do not touch the River Thames Jump back to your train, and defend Ned if needed to finish the memory. After searching the last crate, you will have to detach the final wagon, then jump back to your train. HOWEVER, before searching a box, detach every cart along the way before opening crates, so as to get Detach the reinforcement wagons - Complete. You will have 3 markers here, which are boxes you need to search. Wait till your train is alongside the enemy train, and jump onto it. After the cutscene, you will be on a train. Once you have escaped, you will get Do not kill a single policeman from the convoy. Now just incase, if any police carriages chase you, hit them once to slow them down, then just escape them, as I'm not sure if these count as convoy kills. Now try to just drive it away, as we CAN NOT kill any policemen here.
Now it may stop, if not, you'll need to hijack the convoy, and get in the coach that Ned is trapped in.