I started my career as an engineer at armaments firm Vickers but left after a few years to become a banker. They aren't so different. Think of words like leverage, gearing and synergies. If you can solve a mechanical problem you can solve a financial one.
Harvard Business School has a zero sum grading system, so to get into the top 10%, like I did, you just need to make sure 90% of your peers do worse than you do. Your colleagues are your competitors. They can be your friends too, but you need to remember both elements are always present.
I stayed at merchant bank Lazard for 34 years. Sometimes I thought this showed no imagination, but I could so often say that if they'd sold tickets for what I'd seen that day, I'd have bought one. Instead, I was well remunerated of course, which is even better.
The City was completely different in the 1970s. People wore stiff collars and never used your first name. Our chairman, the austere Highlander Sir Ian Fraser, once roasted me because there was a full stop missing in a piece of work. If a client saw that, they'd doubt the quality of the rest of it. I learned my lesson. If people send me sloppy work I send it back.
It was a huge responsibility being chairman of Barclays during the financial crisis. Anyone who says it wasn't terrifying wasn't there. I'm proud we survived and give very high marks to the then chief executive John Varley for that. He was courageous, creative and cool, which was just what we needed at the time.
The Libor fixing scandal was every chairman's nightmare. It should never have happened. We spent £100m and sent 22 million emails to get to the bottom of it. I resigned because I was the person ultimately responsible for our reputation. You could think that if a senior departure was demanded, then the chief executive was more valuable, but that wasn't the reason I did it.
A chairman’s job is to champion the chief executive, though that doesn’t mean you may not have to fire them if needed. I’ve been lucky. I’ve worked with a lot, and can't think of a single one I didn’t respect enormously. No two are the same, so the way to manage them isn’t the same. You have to be a chameleon.
I split my time between the chairmanships of PA Consulting and the Board of Trustees of the Royal Botanic Gardens, Kew, making my experience and contacts available when appropriate. Gardening is excellent therapy. It takes away your cares and at the end you have the satisfaction of looking at something very different from how it started
London is in a golden age. It's full of interesting people. But its success will produce strains. The population's gone from six million to 8.5 million in 15 years. It's okay now but it will become increasingly difficult to manage.