There are two targets in this Templar Hunt with one patrolling the waterfront and the other located on a boat on the southern end of the restricted area.

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Use Eagle Vision to tag enemies/targets (left). Allow one of the targets to attack you and the police will attack them (right).

Fortunately, the optional objective for this memory is actually fairly easy to do once you know how to go about it. For the record, I think the fellow patrolling the waterfront is the better option for the optional objective, but it can be achieved with either. Essentially we need to get one of the targets to detect and attack us – let them initiate the fight – and this will trigger the policemen nearby to come and attack. It’s a good idea to sneak around and thin out the Blighter numbers before doing this though so that the police stand a fighting chance!

Use the policemen to kill one or both of the targets (or do in the second one yourself) and once both of them are pushing up daisies, escape the area to complete the activity.