REACTION

EU affairs ministers and ambassadors from member states gather in Luxembourg by 10 a.m. (0800 GMT) for previously-scheduled talks that will provide the first chance for many to react. A regular EU summit has been pushed back to next Tuesday and Wednesday, when Cameron may trigger Article 50 of the EU's treaty, the legal basis for a country to leave, setting in motion two years of divorce negotiations.

Even less clear at this stage is what sort of relationship Britain will seek to negotiate with the EU once it has left.

To retain access to the single market, vital for its giant financial services sector, London would have to adopt all EU regulation without having a say in its shaping, and pay a substantial contribution to Brussels coffers for market access, as Norway and Switzerland do.

EU officials have said UK-based banks and financial firms would lose automatic "passport" access to sell services across Europe if Britain ceased to apply the EU principles of free movement of goods, capital, services and people.

Aside from trade, huge questions now face the millions of British expatriates who live freely elsewhere in the bloc and enjoy equal access to health and other benefits, as well as millions of EU citizens who live and work in Britain.