Time slots are allocated in half an hour sections, however, they understand that sometimes you may be running late. Your time slot will allow you half an hour to arrive and enter the Dockyard so a 10 am till 10.30 am slot means you can arrive between 10 am and 10.30 am. If you do miss your time slot, they will ask you to wait and will do their best to fit you into the next available slot. The staff at their visitor center will be on hand to help should this be the case.