It is often said that your personal value is not what you know, but who you know. This is powerful motivation for recent graduates to build their personal networks. But some of us may conclude that we already have enough friends and contacts – the challenge is making the best use of those that we already have.

Mathematics supports this argument. If you have been in business more than 20 years, you probably have more than 150 close contacts – people you like and respect and would recognise if you bumped into them out of their work context. If you add to this all the people in their close networks, this aggregates to potentially more than 20,000 agreeable and interesting people.