“The 250th anniversary of the founding of the British Museum has been a low-key affair. Three years ago the plan was to honor the occasion with the opening of a new $55 million Study Center in a nearby building. But lacking money the museum sold the property. So instead of a glitzy inauguration, this month’s anniversary festivities are built around music, dance, lectures and exhibitions. Yet for all that the mood inside the museum’s sprawling neo-Classical home in Bloomsbury is not glum. Credit seems due to Neil MacGregor, 56, who last year took over as the museum’s director.”