Britain's ongoing refusal to give Gibraltar back to the Spanish has resulted in a last-minute snub against the Queen.
Spain's Queen Sofia has pulled out of Elizabeth II's Diamond Jubilee lunch at Windsor Castle after earlier saying she would attend.
A Spanish royal family spokesperson said in a statement that the visit would be inappropriate "under the current circumstances" - thought to relate to Prince Edward's planned visit to Gibraltar in mid-June.
Three centuries of simmering tensions over the Rock, which Britain has retained long after its naval use as a strategic base at the entrance to the Mediterranean has passed, have been increasing recently.
Current disputes centre around the use of waters around Gibraltar, which Spanish fishermen want access to.
The election of a right-wing government in Spain is thought to be behind the hardened stance on the Rock.
But tensions within the Spanish royal family may also have had something to do with the snub.
Queen Sofia and her husband King Juan Carlos are effectively separated and their golden wedding anniversary passed last week without any kind of acknowledgement.
In Britain Diamond Jubilee celebrations are in full swing. Tomorrow's lunch is expected to feature controversial guests including the king of Bahrain, whose suppression of pro-democracy protests has attracted much criticism in the west.