The yo-yo price of the Pound as no-deal Brexit has become more or less likely over the past few weeks demonstrates that Brexit is very much not priced in.

No-deal would be so damaging that the markets don't think it's going to happen, and that props up the Pound. So it takes a lot of political madness to convince the market that the worst is happening, and that's when the Pound starts plumbing historical depths. Then the madness recedes, and the Pound bobs back up again.