The price of staying alone also involves a financial cost of refusing to belong.

"The British position does not allow those persons concerned to continue to live their lives as they do today".

That's according to the EU's top Brexit negotiator, Michel Barnier.

He says the European Court of Justice must have unconditioned jurisdiction to guarantee citizens' rights.

He also said it is essential that the UK recognises its financial obligations in the deal being arranged.

Barnier explains that if Britain did not accept it has some financial obligations, there would be no basis to discuss other issues.

The biggest sticking point appears to be the EU's insistence that Britain settles its outstanding financial obligations. 

When asked about Boris Johnson's suggestion on Tuesday that the EU could "go whistle", he joked that the only sound he could hear was a clock ticking.