While the pair have previously been photographed together outside Kate's home, the meal marks their first public sighting together since rumours first surfaced.
The reported couple were first linked in January, but it is said they have gone to great lengths to keep their so-called romance a secret.
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"We went behind-the-scenes in the kitchen earlier today to see preparations being made for lunch and tea.
Pots dating back to Queen Victoria's day were being used for cooking." After lunch Queen Letizia and King Felipe VI will view an exhibition in the Picture Gallery from the Royal Collection relating to Spain.
It is likely that Meghan will be a regular visitor to the private members' club's London outposts, including Soho House 76 Dean Street, Shoreditch House, Little House Mayfair and Electric House on Portobello Road, only a mile away from her new home at Kensington Palace.
Should they wish to get away from the city the couple can also visit Soho Farmhouse in the Oxfordshire countryside, where they are said to stayed together before their relationship became public knowledge.
King Felipe will deliver an address, before the royal couple attend a reception with members and invited guests on Wednesday evening.
Steel Yard can personalise your event and cater to your every need.Your bespoke event can be powered by our professional events team who can assist in planning your perfect event! Based in the City of London, our versatile events space is a blank canvas suitable for any event hire.Originally, this grade 2 listed building hidden under Cannon street station was once an economic powerhouse dating back to the 1800’s. We have showcased some of London’s finest parties and corporate events, from some of the world’s most prestigious DJ’s or even intimate’s events to fashion shows, the phenomenon is a never-ending wonderland!The Spanish royals tucked into prawn salad during their State Visit The Spanish royals will also have a taste of a classic British sandwich; smoked salmon and cream cheese sandwiches served on seeded bread, all with the crusts carefully removed.A further course can be seen being prepared in large saucepans, which have been revealed to date back to Queen Victoria's reign.STORY: The Queen welcome's Spain's King Felipe and Queen Letizia to the UK Although the meal was private, we did get a behind-the-scenes glimpse at what the royals tucked into for their lunch courtesy of The Royal Family Instagram account.