When Einstein submitted his six-page PhD thesis, his examiners were impressed with his ideas but asked him to ‘write a little more’. He took it away, thought about it for a week, added one sentence and resubmitted his thesis. It passed.

A theory doesn’t have to be long and complicated to be profound. Drucker summarises the purpose of a business and the role of managers in under 75 words. Yet these few words have been the basis for much of the management thinking and writing for the past 60 years. And he didn’t even have to add an extra sentence.

The most consistent message that comes across in this section is that management theories are often contradictory: writers can’t even decide if it’s better to batter staff into submission with a blunt instrument or wrap them in cotton wool. But that’s OK because people and situations are infinitely variable and you can’t expect one approach to be successful in every situation or with every person.

Always remember that you’re a manager not an administrator. Your job is to organise and coordinate the work of your staff, not fill in forms. If you’re new to management, you must act, think and talk like a manager. Look again at what Drucker has said is the role of the manager. That’s your job description and it describes the nature of your work whether you are a junior manager or a managing director. Whenever you find yourself spending too much time on non-management tasks you need to reassess your priorities.

Finally, some managers are in love with their own voice. Remember: you have two ears and one mouth; clever managers use them in that proportion.