I am standing in the workshop of the Bethlehem Icon School staring at a nugget of limestone the colour of honeycomb. It has been hewn from rock somewhere along the road to Jericho and will shortly be ground into a fine powder with a pestle and mortar. Next it will be bound with the yolk of an egg and thinned with drops of vinegar or vodka.

The result will be yellow ochre. It’s a colour that has been produced in much the same way since painting began.