It's a pun.
Assassin's Creed Syndicate Sequence 4 - The Create Escape
- Search the Templar chest
- Defend the Templar chest
To start this mission, travel to the train hideout and visit the carriage closest to the engine, approaching the desk on the right.
When you're back in action, use the Rope Launcher to go over the ships and up onto the building to the west. Climb to the peak of the roof and look across to the north to spot a sniper; use the Rope Launcher and an air assassination to take him out. Look back to the south and you'll spot another sniper; rinse and repeat to take him out.
Now that the most dangerous threats are out of the way, feel free to just drop down and start fighting if you like. The true assassin would probably keep thinning their ranks stealthily, though; just sayin'. Once you can get to the cart, search the chest inside.
After the eventful few seconds that follow, you'll need to snipe away pursuers as Jacob drives the cart out of danger. This isn't too hard, but there are two things to watch out for. First, make sure you reload whenever you get a moment, so you don't click on an empty chamber when you need it. Second, you need to press the dodge button when you see an icon indicating enemy fire.
No matter what you do, some guards will board the cart - so be prepared to fight them off immediately. The quicker the better.
Eventually you'll be given a ten second timer to jump out of the cart and get to a waypoint; it's nearly impossible unless you abandon ship as soon as you're prompted to. The mission ends when you successfully reach the waypoint.