The 25th anniversary of the proclamation of King Juan Carlos was marred yesterday by the killing of a former socialist minister, Prof Ernest Lluch.
Officials have no doubt that the murder was the work of the Basque terrorist movement ETA, which has killed 21 people, three of them socialist politicians, since it called off a 14-month ceasefire at the beginning of the year.
Prof Lluch (63), health minister from 1982 to 1986 in Mr Felipe Gonzalez's first government, was shot in the head as he was parking his car in the garage beneath his Barcelona apartment.
His body was not discovered for two hours later after the terrorists had detonated their getaway car to eradicate any fingerprints in waste ground 50 yards away.
Mr Lluch became involved in democratic politics while a student, and was arrested on several occasions and twice expelled from university.
He became a socialist deputy in the first democratic parliament in 1977 and remained in the parliament until 1989 when he left active politics to return to his academic career.
Although a Catalan, Mr Lluch had a holiday apartment in San Sebastian and considered the Basque Country his second home. He frequently spoke out in favour of dialogue in the region.
After the breakdown of the ETA ceasefire in January some of his friends suggested he might be a target for a terrorist attack and should not visit the area. He refused their advice saying: "If I didn't continue coming here I would never be able to look my Basque friends in the eye again."
The official celebrations marking King Juan Carlos's 25 years on the throne began with a minute's silence in memory of Prof Lluch.
The royal palace announced the cancellation of a reception as a sign of respect for Prof Lluch, but the king and queen received deputies, senators and former political leaders, including Mr Felipe Gonzalez and the former Communist leader, Mr Santiago Carrillo, in the parliament yesterday morning.