The King and Queen of Spain took tea with the Prince of Wales and his wife, Camilla, the Duchess of Cornwall in London on Wednesday.
The Spanish royals were hosted at Clarence House in central London.
The three-day visit by King Felipe VI and his wife, Queen Letizia, comes amid a brewing dispute about what Brexit means for the future of Gibraltar, a tiny, rocky territory at the tip of the Iberian peninsula that Britain has controlled for three centuries against Spain's wishes.
The two countries are also trying to resolve the status of thousands of expatriates facing uncertainty over their rights once Britain leaves the EU.
Yet there was no sign of discord as the Spanish royals arrived earlier on Wednesday at Buckingham Palace, with Britain treating them to the full pomp and pageantry traditionally rolled out for visiting heads of state.
Later, addressing both houses of Parliament, Felipe said Spain was saddened by Britain's decision to leave the EU but respects it.
He urged the two governments to guarantee citizens' rights after Britain's withdrawal - a key sticking point in Brexit talks.