They had a pretty good idea of when it would happen. And once it started, it took a while. Advance notice had gone out to mariners so that they would have time to move their vessels in or out of the gates before they swung shut. Saskia wanted to be there for at least part of it, as the capstone of her disaster preparedness jihad. So she went out a bit early and, to kill time, did an informal drive-by inspection of the nearby Maasvlakte.