The x-ray in the centre shows considerable changes across the painting, made by the original artist during the construction of the composition. For example, the foot on the left was moved and a window was painted beneath the column and the coat of arms. The holes made by the point of the compass can be seen in the decorative balls on the chair. Fine lines of carbon-based underdrawing can be seen in the hands and temples in the digital infrared reflectogram on the right and there are also some changes of position in the fingers and cuff.

© National Portrait Gallery, London