The move began a period of talks designed to establish how the UK will interact with the European Union (EU).
It also gave UK-based EU agencies like the European Medicines Agency (EMA) just two years to prepare to move to a new member state.
The EMA is mulling potential new locations and last week it outlined its best and worst case post-Brexit scenarios.
Nineteen EU member states have bid to be its new home according the EMA, which asked its 700 staff to rank the competing cities based on how likely they are to keep working for the agency after it relocates.
The five leading candidates have a likely average retention rate of 73%, while in eight cities the EMA would only be likely to keep 18% of its staff.
In the best case scenario, in which it moves to one of the cities in which it is likely to retain 73% of its staff, the EMA said its drug approval processes and safety monitoring activities would be impacted for two to three years.
The agency also predicted that even if it does keep around three quarters of its staff, public health programmes – like initiatives focused on combatting antimicrobial resistance – will move at a slower pace.
At a retention rate of 54% - which is what the EMA expects to achieve in five of the candidate cities, based on the staff survey – the agency said approval processes are likely to be disrupted for up to five years and warned that “public trust in the system” will start to erode.
The EMA’s worst case scenario is if it moves to one of the eight cities in which it is likely to retain less than 30% of its staff.
In such circumstances the agency said there would be an “unravelling of the EU single market for medicines” with the lack of centralised authorisations limiting drug availability, increasing reliance on imports and putting patients at greater risk of side effects and death.
An EMA spokesman told us "The decision on EMA’s new location will be taken by the EU Member States, not by EMA."
He added that the selection procedure, which was adopted by the European Council in June "foresees that EMA will be consulted on the technical requirements in the Commission’s assessment of Member States’ offers, which is due by 30 September 2017.
"EU member countries will hold a political discussion at the General Affairs Council on 17 October, the decision is expected to be made at the next General Affairs Council meeting on 20 November."