In the early 15th Century, King Władysław II Jagiełło invited the Ruthenian master Andrej and his school to the Lublin royal castle to paint a mural that covered the Holy Trinity chapel from the floor to the vault. When the work was finished in 1418, Andrei signed his name on the arch and moved on, probably to the next commission.What the master left in the kaplica was nothing short of splendid. The icons and scenes combine the Eastern style of representation with the Gothic art and architecture of Catholic Poland. We came close to losing this unique example of sacred art, however.By the 19th Century, the paintings had become so damaged by age, moisture and soot (from the altar candles) that somebody decided to cover them in plaster when the castle was turned into a prison. Even that did not last long. In 1899 a painter discovered a fragment of the old murals behind the crumbling plaster by chance. The intermittent uncovering and restoration of the paintings took nearly a hundred years while the conservators worked to stabilise the environment within the chapel, and the entire project was completed just 20 years ago.Today, the interior of the Holy Trinity chapel is now climate-controlled. As a further measure, visitors are let in for just 20 minutes every hour. The murals should hopefully last a lot longer now, having survived 600 years of fires, wars and occupations.