Theresa May has been told to protect the interests of Spanish people living in London by her counterpart in Madrid, Mariano Rajoy.
Mrs May and her entourage met Rajoy and the Spanish delegation for around 25 minutes at the start of the EU summit currently being held in Malta.
According to Spanish newspaper El Pais, Rajoy asked May to ensure the Brexit process is carried out "quickly, with a constructive approach and positively."
Sources close to the discussion also said the pair agreed on the importance of "not harming the interests of those Spanish and British citizens" living as ex-pats in the respective countries.
Spain is home to around 300,000 British ex-pats, the majority elderly people living in retirement communities, while there are around 200,000 Spanish emigres in the UK, many of them young professionals working in London and other big cities.
Britain is also the biggest source of tourism for Spain, with around 15.5 million British people visiting the country in 2015.
Mrs May unveiled her Brexit White Paper yesterday (Thursday), expanding on the points outlined in her Lancaster House speech last month. She has offered a conciliatory approach towards migrants currently living in the UK, although Home Office minister Robert Goodwill has suggested Britain could set an annual limit on new migrants from the EU once Brexit is complete.