What Happened to the London Underground During the Smog?

On the morning of december sixth, the smog was so thick that the sun could not beak through it. Invisibility was so bad that taxi and bus drivers couldn't see to drive. People abandoned their vehicles because they either couldn't see or couldn't get through the resulting gridlock. This completely overloaded the london underground, which was spared from the smog by virtue simply of being underground. Boat traffic on the thames ground to a halt as did air traffic at huthro airport flights were either cancelled or diverted to other airports outside of the smog. And this smog disrupted the train schedules as well. One ferry across the english channel was delayed by 15 hours