In his post at Buzzfeed on why our European cousins can’t find the jihadis in their midst, Mitch Prothero suggests that it’s a combination of inefficiency, political correctness, and the fractured nature of their societies.
Based on my experience in Europe, their investigators probably only work from 9-5 with scheduled breaks for lunch and coffee and they don’t work at all during the month of August. I’d think those would pose problems.