Gordon Brown

If you take energy and climate change, you really cannot deal with the problems with energy and climate change without European co-operation at a high level. If you take digitalisation, it's an obvious area where European co-operation can actually make a difference.

Whenever you have dynamic interactions between 300 million people and the American economy acting in really complex ways, that introduces a degree of almost chaos theory to the system, in a literal sense.

Set your sights high, the higher the better. Expect the most wonderful things to happen, not in the future but right now. Realize that nothing is too good. Allow absolutely nothing to hamper you or hold you up in any way.