Christo once wrapped up the Reichstag, suspended a curtain across a Colorado valley and covered up the Pont Neuf in Paris. Now, six years after the artist’s death, a London gallery is to create a monumental installation he designed in 1968, using a detailed scale model and drawings that had been presumed lost until their chance discovery. Christo had imagined a vast, internally illuminated suspended form, like a cloud, but technical constraints meant the plan was never brought to fruition. Package on a Ceiling was conceived for the Institute of Contemporary Art in Philadelphia. Now its first realisation will fill a huge exhibition space at Gagosian London in a collaboration with the Christo and Jeanne-Claude Foundation. The piece will fill the full volume of the space – 16 metres long, 10 metres wide – descending to just above head height. Christo and Jeanne-Claude at the National Gallery of Art in Washington in 2002 with photographs of some of their work.…