The UK is rolling out the red carpet for King Felipe VI and Queen Letizia of Spain, sprinkling pomp and glamour over some deep-rooted tensions.
Brexit and the centuries-old dispute over Gibraltar might suggest that UK-Spanish relations are between a Rock and a hard place.
But the 12-14 July state visit could send a sunburst through those clouds. The royal couple were due to arrive in London on Tuesday.
Both royal lines are descended from Queen Victoria - something to celebrate, in tough times for both countries.
Three years of trouble
This visit is nothing if not a survivor, having been called off - once in 2016, when Spain endured 10 months of political crisis without a government, and again this year, when UK Prime Minister Theresa May called a snap election in June.
"These have been times of great difficulty on both sides, with the double cancellation telling its own story," says Ana Romero, a leading Spanish journalist and royal observer. She wrote a book - Final de Partida (End Game) - about the strained personal circumstances surrounding the abdication of King Felipe's father, Juan Carlos.
Ms Romero says King Felipe's reign has been three years of "permanent difficulty", including a fraud trial in which his sister, Princess Cristina, was eventually acquitted, while her husband Iñaki Urdangarin was sentenced to six years in jail.
Almost as damaging were supportive text messages Queen Letizia reportedly sent to a suspect in another corruption case.
"Now after three years of hard climbing, it is as if Felipe and Letizia have reached the bright summit, because the British monarchy represents the height of royal protocol," Ms Romero says, before adding that both countries face great problems.
Spain is still emerging from an economic crisis that has seen confidence in institutions plummet due to corruption scandals.
British politics entered a turbulent period with last year's referendum vote to leave the EU. Brexit remains shrouded in uncertainty.
Many of Spain's leading companies have made bold moves into Britain, including Santander bank and Ferrovial, an infrastructure group that owns Heathrow's operating company, among other UK concerns.
Brexit is also a worry for the many citizens living in each other's country and for those with investments at stake.
The almost 300,000 British citizens registered as residents in Spain, and many more who come and go, are concerned about their healthcare and pensions, says Anne Hernandez, leader of Brexpats in Spain, a group with more than 4,000 members.
The Rock - a sore point
While British diplomatic sources say they consider Spain an ally in negotiating relatively benign terms for Brexit, they also admit they are concerned about Madrid's insistence on re-examining the status of Gibraltar - an already delicate equation.
This is especially the case after the European Council included a clause in its guidelines for talks, stating that no agreement on the EU's future relationship with the UK would apply to Gibraltar without the consent of Spain, giving Madrid a potential veto.
All eyes will be on King Felipe when he speaks to UK parliamentarians on Wednesday, to see if he emulates his father Juan Carlos. As king back in 1986 Juan Carlos raised Spain's claim over the Rock when addressing MPs and Lords, on the last Spanish state visit to the UK.
The signs are that Felipe is prepared to broach the issue as he did before the UN General Assembly last autumn. Describing Gibraltar as the last colony in Europe, Spain's king invited the UK to "put an end to this anachronism".
King Felipe, who will also have a private meeting with Prime Minister May, is considered a consummate diplomat, having been patiently groomed for the job by representing Spain in Latin America and elsewhere for almost two decades before his coronation.
He also proved in 2004 that he was his own man by marrying the TV journalist Letizia Ortiz, a commoner and divorcee.
For the first time Prince Harry, 32, will have an important ceremonial role, escorting Felipe and Letizia to Westminster Abbey.
He will also attend a grand state banquet, after the Queen has welcomed her Spanish guests to Buckingham Palace on Wednesday.