Holbein's Ambassadors, National Gallery, London W1 (0171-747 2885)

In the face of the young Turks of TV insisting on fast editing, "sexy" graphics, and catering to the attention span of a disinterested gnat, the odd old-fashioned, unflashy, thoughtful arts documentary slips past the opposition. The BBC's portrait of the years of painstaking research and mind-bogglingly detailed restoration of Holbein's famous painting made completely gripping viewing. Even if you missed it you should see this great work returned to its true splendour now that the dirty layer of 19th-century varnish has been removed. It's as if a veil has been lifted from in front of what was always a startling double portrait. This free exhibition is a marvel and a magnificent tribute to the determination and dedication of the gallery staff. This is why we pay our taxes.