The decision of the United Kingdom to leave the European Union will redefine British relationships with the rest of the European continent for decades to come. When London decides to activate Article 50, the arduous and difficult process will begin.
Although currently there is only uncertainty, both sides of the Channel are beginning to take their positions as they begin the negotiations.
Brexit could greatly affect British expats (Brexpats) in the same way that EU expatriates living in the UK are affected.
The UK government recently stated that these expats would have to apply for long-term visas in order to live in EU countries. These possible measures would affect those who work abroad as well as pensioners.
In the first instance, the visa application process would remain the same as that for non-Europeans applying to live in the EU, and the very term 'British expats' - a euphemism often used to refer to privileged immigrants - would essentially cease to be used, in favour of 'British immigrants'.
Obviously reciprocity will apply in the UK and EU immigrants will need to go through a similar process, but the reality is that there is not a symmetrical relationship with all countries.
Thus, most Brexpats live in Spain and equally there are many Spaniards living in UK - this will most likely help secure privileges between the two countries in bilateral negotiations, but this cannot be the case for all countries.
Moreover, it may become more complex for UK expats to work in the EU if host countries apply stricter regulations for them to establish businesses.
There is a possibility that expats will forfeit their right to work in the EU automatically, and a process similar to the US Green Card or Australian Blue Card will be introduced.
The reality is that there are currently 1.2 million British citizens living in EU countries, with Spain being the most prominent destination. So what about those who are already living abroad?
We advocate a two-tiered negotiation: the current multilateral approach with all EU countries involved through EU institutions to keep current status under the European Economic Area Treaty, a similar arrangement to Switzerland; and a bilateral approach on a country-by-country basis, to ensure reciprocal privileges are maintained as far as possible for existing expats and avoid introducing barriers to entering new countries.
Obviously there will be grounds for Brexpats to consolidate 'pre-Brexit acquired rights' under the principle of retroactivity applicable by domestic law in all jurisdictions.
However this cannot be applied for automatically and Brexpats will need to appoint immigration legal representation in each individual case.
Thus, the issue of visas and residence permits will be one of the most important issues in the negotiations of Brexit. It is estimated there are about 300,000 Brits living and working in Spain, of which 20 per cent are pensioners in the Costa del Sol.
With UK pensions being used to fund Brexpats' lives in Spain, any fluctuation in currency caused by Brexit will have an effect on their income.
Following the vote for the UK to leave the EU, the UK government will be the one to decide whether state pensions will remain protected from wage or price inflation, or whether the pensions will be frozen, as is the case for retirees in Canada.
Currently, the visa system in Spain is governed by the Organic Law 4/2000 and its implementing regulation, promulgated by Royal Decree 557/2011.
Applicants (excluding members of the EU or countries in which the Schengen Agreement applies) must do so in person or by representative and pay a fee of €60 (£50) not subject to return. The visa entitles the holder to stay in Spain for up to three months.
As the London-Brussels negotiations are not expected to be activated until January 2017, the legal status of Brexpats (present and future) remains the same for now, although there is still a lot of uncertainty about next steps.
Spain's prime minister stated that whilst all is still under negotiation, expats would enjoy the same rights as they have had up until now as EU citizens. After Britain exits the EU, these rights will depend on the agreement that the UK comes to with the EU and each member country.
As stated above, we urge the British government to engage sooner in bilateral negotiations with specific countries and in particular to embrace a dialogue with Spain to ensure Brexpats' rights are protected and secured for the future.
Leon Fernando del Canto is a barrister in Spanish and English law and a partner at Del Canto Chambers.