A modern container ship arrives at the breakwater doing four or five knots and immediately becomes the least maneuverable object in the harbour. That’s the part people miss when they watch the process. The ship isn’t being helped along. It has effectively stopped being able to steer itself, and three small boats are now doing the job its 60,000-kilowatt main engine can’t. The reason is that a rudder is a wing.

A mid-size container ship with working bow thrusters, a competent master and a pilot on the bridge does not, on a calm afternoon, need two tugs to leave a harbour. It takes them anyway. The reason is not seamanship. It is that the port’s marine services regime priced a low-probability failure and decided the shipowner would pay for it on every movement, every day, whether the wind blows or not.