The costs of a visit by the king of Spain, Juan Carlos I, and his wife Queen Sofia in 1986 included a £3,009 bill for a stay by the royal entourage at Dromoland Castle.
There was also a £2,300 bill for the Berkeley Court hotel and a bill of almost £7,000 for a helicopter trip.
A delegation of Spanish and Irish officials took 21 rooms at Dromoland on the third night of the state visit from June 30th to July 2nd, which also included visits to Monasterboice and Newgrange.
Eighteen single rooms at the luxury five-star hotel in Co Clare cost £75 each at 1986 prices and three twin rooms were charged at £100 each.
Dinner for the delegation cost £1,242, with wine and drinks costing £764 in total. Lunch for the group cost £371.
The bill from Irish Helicopters for the royals’ flight to Clare from Dublin and a tour of the county was some £6,886, including 3.6 hours flying at a cost of £1,850 per hour, according to invoices from Department of Foreign Affairs files. Booklets and musical programmes for the visit cost a further £1,061. The cost of official photographs was £1,528, and the traditional group Na Casaidigh were paid £230 for their performance during the visit.
The royal couple were also entertained by the taoiseach Garret FitzGerald at a lunch in Iveagh House, and hosted a reception for the Spanish community at the ambassador’s residence.
President Patrick Hillery paid tribute to Juan Carlos during the visit for the "leading role" the king had played in "encouraging reconciliation and the peaceful evolution of democracy in Spain".
Tributes were also paid to the king for his role in overthrowing the attempted coup in the Spanish parliament in February 1981.
For his part, the king referred to the historic links between Ireland and Spain going back to Celtic times and said that Spain had "consistently upheld the inalienable right of the Irish people to their independence".
The files also reveal that gardaí proposed to offer weapons permits for four named officers in the Spanish delegation.
Guidance to Dublin
Irish embassy officials in Madrid issued guidance to Dublin ahead of the visit on potentially politically sensitive issues, including the question of Gibraltar.
"I must request you earnestly to be so good as to bring to the attention of Political Division in the context of this telex that Gibraltar is a most sensitive bilateral issue with the United Kingdom and that this contentious issue has overtones of a family feud, ever since the heir to the British throne honeymooned there.
"The royals concerned are all descended from Queen Victoria and this action added personal affront to a contentious issue of national sovereignty."
Political issues that might find themselves on the agenda included internal terrorism, including the "Basque problem", which the Spanish tended to equate with Northern Ireland, diplomats said.
The only potentially serious issue of contention was that of fisheries.
“Perhaps we are more likely to wish to raise this than are the Spaniards,” one telex read.
Advising in April on the particular interests of the Spanish royals, embassy officials said Her Majesty would be delighted with the archeological aspects of the visit as her professional studies and interest lay in this area.
The royal couple would also be very interested in Celtic remains. The king liked shooting, but the queen did not, the note added.
The Spanish royals would only travel in a twin-engined helicopter and embassy notes to Dublin said the king should be invited to take the controls during the flight to Co Clare.