The world has lost a giant. Prof Stephen Hawking, the Galaxy’s best-known scientist and most unlikely cultural icon, died on Wednesday 14 March at his home in Cambridge. I’ve spent the days since speaking to those who knew him and one clear theme emerges. Hawking was a stubborn man. Of course, he was funny and smart, that was clear for the world to see. But perhaps, to those of us watching from afar, his radiance hid the vital ingredient to his genius: true grit. Hawking was determined to never let his condition slow him down. Sometimes literally: Hawking broke his leg on his 60th birthday after driving too fast off a kerb. He travelled the world, and even had a taste of zero-gravity. It was this same resolve that would drive him, sometimes to the exacerbation of his colleagues, to spend years writing and rewriting his books so that he could share the elegance of the Universe with others. And ultimately it was this sheer strength of will, rather than a single eureka moment, that would propel him through the maths that underlined his work. Funnily enough, Hawking shared this personality trait with the most famous scientist of the last century, Einstein, who wrote of himself: “If I have a gift, it is that I am as stubborn as a mule.” So if you learn anything from Hawking, I suggest that it needn’t necessarily be the nature of black holes or the origins of singularities, but that sometimes a little stubbornness can be a useful thing.