I was at the Painted Hall, Greenwich for an afternoon event on 13 January, which was arranged by the Old Royal Naval College.
Conservation work on the west wall of the hall recently began. The ORNC are involving the public in the project. As part of a small group me and a few friends took the opportunity to withess Thornhill's stunning work up close. We were taken up the scaffold to a platform just below ceiling level (11 metres), where we were shown the restoration work being carried out by the team of conservators. I would recommend the experience to anyone, if they are visiting the Greenwich area.
More details, and a interesting short video are available on the ORNC website:
http://www.ornc.org/conservation/projects/painted-hall-conservation