A hung parliament is the nightmare scenario for May. It would constitute a massive personal failure and undoubtedly make for great domestic political uncertainty at the worst possible moment for Britain.
If Mrs May fails to get the thumping majority she hopes for, her position will be a lot less secure than before she called the snap election.
Mrs May has made this campaign particularly personal and a failure to secure a large swathe of new Tory MPs would be seen a failure of hers. This risks throwing open a Tory leadership contest and the prospect of a hard-line Brexiteer in charge. Boris Johnson is waiting in the wings. A hung parliament could easily see Jeremy Corbyn become prime minister – investors simply wouldn’t know where they stood.