It will have taken five years, instead of the planned two, and cost €52m but there will be celebrations in Paris this summer when the celebrated Picasso Museum reopens after a massive renovation.
The transformation of the magnificent 17th-century Hôtel Salé, a baroque mansion in the Marais district, one of the oldest areas of the French capital, has been controversial because of the time it has taken and the considerable budget overspend.
However, the museum's president, Anne Baldassari, said during a tour of the site on Tuesday that the result would be worth the wait and "do justice to the extraordinary collection" of Picasso masterpieces.
As workers rushed to complete the new galleries and lay out the new garden, complete with massive pergola, everyone insisted the building would be ready for the Picasso collection to be installed at the end of May, ready for opening in June.
The modernisation of the Hôtel Salé was expected to cost around €30m (£25m) when the museum closed in 2009. Part of the overspend is due to the purchase of two neighbouring buildings to house offices, freeing up more space for exhibits.
The transformation will more than double the space for one of the world's most extensive collections of the Spanish artist's work, and allow more of the 5,000 paintings, drawings, sculptures, photographs, ceramics and archive documents in the museum's collection to be shown to the public. Until now, only a fraction could be shown at any one time.
The space open to the public has increased from 1,600 sq metres to 3,800, creating 37 permanent galleries, a 95-seat auditorium, a workshop for school groups, a terrace and a cafe. The garden is being redesigned and a roof garden, which will not be open to the public, is to be built.
Masterpieces on display will include not only Picasso's works, but paintings in his collection including ones by Matisse, Renoir and Cézanne. All the Picasso works have been cleaned, restored and reframed.
Museum officials hope the number of visitors each year will jump from 450,000 to 850,000.
The Picasso Museum first opened in Paris in 1985. Most of the exhibits were bequeathed to France by Picasso's heirs, according to his wishes, on his death in 1973. His widow, Jacqueline, donated a substantial number of works, and friends gave other legacies and donations. More than 1,000 exhibits have been bought by the museum since 1985.
The renovation work was constrained by the listing of the Hôtel Salé as a historic building, and by strict health and safety rules, including an overlooked notice of non-conformation to fire regulations dating back decades. "Everyone seems to have forgotten it, except the fire brigade," Baldassari said.
Architect Jean-François Bodin said the museum would be a synthesis of the traditional and modern. "The challenge of such a project was to develop the space while at the same time respecting a building that is listed," Bodin said.
During the renovations, the exhibits have been touring the world helping to raise €31m to partly finance the work. The French government has paid €19m.
French president François Hollande will inaugurate the new museum a few days before its official reopening on 21 June. As Picasso is reported to have said: "Give me a museum and I'll fill it."