I am indebted to reader Gina Switzer. for bringing to my notice this story of the uncovering of wall paintings in St Cadoc's, Llancarfan in the Vale of Glamorgan, south Wales. Experts were called in after the architect noticed a single red line high up close to the rafters on a wall where a tiny patch of an estimated 27 layers of whitewash had fallen away from the plaster underneath. Gradually the whitewash was removed to reveal on one side of the church a large, floor-to-ceiling painting of St George and the dragon, and pictorial portrayals of the seven deadly sins. The church was found on the site of a monastery around 1200 and these painting are thought to date from the late 15th century, largely because of the dress of the figures which is contemporary to that period. The photo top left is of avarice and the other details are of St George and the princess.
As usual, what strikes me about this is how during this gothic period the whole church was covered with imagery.
BBC Wales has a video describing the restoration here.
Above: the exterior of the church and, below, the interior before, during and after restoration