Under UV light, the natural resin varnish covering the portrait of Robert Dudley fluoresces more thickly around the inscription at the upper right and along the panel’s edges. This suggests that the old varnish layer was removed in the past, but the person who did this was concerned about damaging the inscription and worked around it. The varnish may be thicker along the edges of the panel because it was cleaned while still in its frame.

There are many small areas of retouching across the painting, appearing as slightly darker patches, but, clearly, much more is seen around the inscription, indicating that it has been reinforced in the past.