Some people don't know how to do what they are told; they have not been used to it, and they neither understand quickly nor are able to turn what they do understand into action quickly.

With an obedient mind one learns the rights of things fast enough; for it is the law of the universe, and to obey is to understand.
"Look out!" cried Mr.Stonecrop, as they were turning the corner into Bloomsbury Square.
It was getting dusky now.

A cab was approaching rather rapidly from the opposite direction, and Diamond pulling aside, and the other driver pulling up, they only just escaped a collision.

Then they knew each other.
"Why, Diamond, it's a bad beginning to run into your own father," cried the driver.
"But, father, wouldn't it have been a bad ending to run into your own son ?" said Diamond in return; and the two men laughed heartily.
"This is very kind of you, I'm sure, Stonecrop," said his father.
"Not a bit.

He's a brave fellow, and'll be fit to drive on his own hook in a week or two.