Across Europe a lot of airtime and ink has been devoted to the pros and cons of Britain leaving or remaining in the European Union. But as the referendum begins, CCTV’s reporter takes a look at the actual procedure that would have to be followed in the event of a Brexit.

In any relationships separation is painful and usually messy.

Though if Britain votes to end four-decades of EU membership on Thursday, it will be Brussels alone dictating divorce terms under an incredibly vague E.U. exit clause written in the belief it would never be used.

Brussels remains tight-lipped about expectations.

"It is always wiser to fix your attention on the first bridge you have to cross which is the referendum instead of speculating about what happens afterwards," said Jonathan Hill, European Commissioner for Financial Services.

Regardless of the outcome there will be an E.U. leaders summit a week after the result.

In the case of a Brexit leaders would discuss a one and a half year timetable for withdrawal, during which the UK would face economic limbo.

"During that period of 18 months there could be an impact of lets say more than one and a half percentage point of growth less due to this process of negotiation," said Philippe Ledent, Senior Economist.

Britain would then have to negotiate extremely complex trade agreements with the E.U. including thousands of regulations covering everything from food to banking.

"If we look at Switzerland, we have negotiated for 30 years with Switzerland with good will on both sides and just as objectively, horrendously difficult and it will remain difficult it will take ages," said Daniel Gros, Director, Centre for European Policy Studies.

The big question is will Brussels take a soft approach to Britain? The signs are not promising.

The president of the European Commission Jean Claude Junker has warned that deserters are never greeted with open arms.

If Britain can ultimately re-negotiate its treaties with Brussels it might mirror Norway, which has to abide by most E.U. rules, but has no power in shaping them.

The only thing that’s clear is that there will be no quick divorce for Britain if a majority votes ‘out’ and that the E.U. and U.K. will be speaking frostily through lawyers for many years to come?