The concept of diligence goes back to the Roman law concept of diligentia, distinguishing two main types of diligence: diligentia quam suis rebus, or the care that an ordinary person exercises in managing his or her own affairs, and diligentia exactissima or diligentia boni patrisfamilia, a more exacting type of care exercised by the head of a family.
Hedley Byrne & Co Ltd v Heller & Partners Ltd  AC 465, per Lord Reid:
The most obvious difference between negligent words and negligent acts is this. Quite careful people often express definite opinions on social or informal occasions even when they see that others are likely to be influenced by them; and they often do that without taking that care which they would take if asked for their opinion professionally or in a business connection.
… Another obvious difference is that a negligently-made article will only cause one accident and so it is not very difficult to find the necessary degree of proximity or neighbourhood between the negligent manufacturer and the person injured. But words can be broadcast with or without the consent or the foresight of the speaker or writer. It would be one thing to say that the speaker owes a duty to a limited class, but it would be going very far to say that he owes a duty to every ultimate "consumer " who acts on those words to his detriment.