The first hours
By the early hours of Friday 24 June, it will be clear if the UK has defied the experts and pollsters by voting to leave the European Union.
If that happens, a shattered David Cameron, his leadership already a matter of speculation, will have no option but to make a statement outside 10 Downing Street saying he will respect the mandate of the British people. The Treasury, Bank of England and the European Central Bank (ECB) will move quickly to roll out well-hidden battle plans to prevent market chaos.
A shocked European political class will find itself grappling with an unprecedented, messy and sprawling divorce that could rumble on for years.
The EU will respond as it does to any crisis, and convene an emergency summit, probably as early as the weekend.
As the morning unfolds it will quickly become clear that although the basic Brexit procedures are set down in law with some clarity, the politics, timeframe and potentially explosive brinkmanship will bring deep uncertainty and new disputes between the Brexiters and Europe.
EU commission officials, for instance, claim the UK will rapidly discover it has put itself in the role of supplicant, and they even talk of throwing the country out on its ear. Jean-Claude Juncker has already warned the UK should remember that deserters are not greeted with open arms.
“It is in our interest to do the divorce as quickly as possible. There’s no appetite for negotiating new terms in the first two years,” one source says.
Others, mainly in the leave campaign, contend that a more stately, considered pace to the divorce is possible. They deny the EU holds all the cards in shaping a new relationship between an independent UK and a jilted Europe.
The high watermark of summer: as the Glastonbury faithful turn their attention to the headliners, and football fans gear up for the knockout phases of the European championships, officials in London and Brussels will be weighing a very different knockout. Rapidly the discussion will move to the processes of Brexit, and the irreversibility of the decision.