When I ask leaders to picture a 'kind leader', I often see a slight hesitation. There's a faint anxiety in the room. People want to say the right thing, but somewhere in the back of their mind is a worry: does 'kind' mean soft? Does it mean being popular at the expense of being effective? Does it mean never pushing hard, never raising difficult things, never making the call that not everyone agrees with? 

It doesn't. Kind leadership is actually one of the most demanding forms of leadership there is. Let me explain what it actually involves. 

A few years ago, I delivered a keynote to a large investment bank in Rome. At the end, during the Q&A, someone asked me what had most helped me build a global business from scratch. 'Kindness fuels everything,' I said. 'If you're kind and people trust each other, then you win. It's as simple as that.' 

The room divided almost instantly. There were people nodding vigorously, and there were people pushing back hard – 'No way! Business is all competition!', 'The ruthless always succeed!' Someone pointed at Steve Jobs and Donald Trump as proof that kindness has no place at the top. 

I've been thinking about that moment ever since. And I've spent the years since gathering the evidence, the case studies and the stories that prove the opposite is true. Kindness isn't the soft option. It's the smart one.