Kings Cross was not as crowded as it could have been, but that’s not really saying much. They still had to push through a crowd of travelers to get a trolley, then race most of the way across the station, weaving around people. At one point, a guard yelled at them to slow down, but Harry tugged Hermione forward, keeping up the pace. The guard gave chase, but a moment later they passed through the portal to the hidden platform, losing him.