Pigeons drop in on Raphael exhibition in Madrid

Gallery staff exploring ways of deterring pests from damaging priceless 16th-century tapestries

The exquisite set of Raphael tapestries currently on display in the grand gallery of Madrid's royal palace has survived five tumultuous centuries of wars, rebellions, bombs, bullets and fire - only to find itself menaced by the more quotidian threat of opportunistic pigeons and their droppings.

The nine tapestries, which depict scenes from the Acts of the Apostles, were created in Brussels in the mid-16th century using the original sketches drawn by the Italian master whom Pope Leo X commissioned to design a set of lifesize hangings to adorn the Sistine Chapel in 1514.