I was very, very thorough, making sure I really understood how that telescope worked, and that it was working properly. I was quite convinced that I wasn't clever enough to be in Cambridge and would be thrown out at some stage. My policy was to work as hard as I could so that I'd know I'd done my best. We now label this as impostor syndrome, but we didn't recognise, and certainly didn't name it, back then.

Curiosity is a form of humility — acknowledging that you don't know everything. Responding to curiosity allows other people to speak freely. Facts and details matter and inform a deeper and deeper analysis that allows you to continually revise and update your plans. This, of course, also means that you are constantly admitting prior mistakes. You need to shed sacred cows, seek out blind spots and challenge the status quo.

I’ve done almost 4,000 operations for brain tumors. I’m thinking of what’s going to happen ten or 12 steps before. I’m anticipating what’s going to happen in the operation, and I’m comfortable with where we are.

I just like to get to the start line knowing there was nothing else I could have done, that there wasn't a single session I didn't give 100 per cent. The physical certainty means you can relax mentally and let the performance come.

Having bought the colours, an easel, and a canvas, the next step was to begin. But what a step to take! The palette gleamed with beads of colour; fair and white rose the canvas; the empty brush hung poised, heavy with destiny, irresolute in the air. My hand seemed arrested by a silent veto.

Painting is complete as a distraction. I know of nothing which, without exhausting the body, more entirely absorbs the mind. Whatever the worries of the hour or the threats of the future, once the picture has begun to flow along, there is no room for them in the mental screen. They pass out into shadow and darkness. All one's mental light, such as it is, becomes concentrated on the task. Time stands respectfully aside, and it is only after many hesitations that luncheon knocks gruffly at the door.

The cultivation of a hobby and new forms of interest is therefore a policy of first importance to a public man. But this is not a business that can be undertaken in a day or swiftly improvised by a mere command of the will. The growth of alternative mental interests is a long process. The seeds must be carefully chosen; they must fall on good ground; they must be sedulously tended, if the vivifying fruits are to be at hand when needed. To be really happy and really safe, one ought to have at least two or three hobbies, and they must all be real.

I hope not too much on them. Well, really, we have to concentrate on the grim emergencies, and when we have solved them, we shall be in a position to deal with the future of the world in a manner to give the best results, and the most lasting results, for the common peoples of all the lands. But one has only a certain amount of life and strength, and only so many hours in the day, and other emergencies press upon us too much to be drawn into those very, very complicated, tangled, and not in all cases attractive jungles.

First of all, you can correct mistakes much more easily. One sweep of the palette-knife 'lifts' the blood and tears of a morning from the canvas and enables a fresh start to be made; indeed the canvas is all the better for past impressions.

You cannot tell from appearances how things will go. Sometimes imagination makes things out far worse than they are; yet without imagination not much can be done. Those people who are imaginative see many more dangers than perhaps exist; certainly many more than will happen; but then they must also pray to be given that extra courage to carry this far-reaching imagination.