From a YT video detail:

It turns out that "Tisha B'Av" falls on the 27th of July this year (2012) and this is the SAME DAY that the London Olympics opening ritual/ceremony takes place.

So the eyes of the world will be on London on 27th of July 2012 for the Opening of the XXX Olympiad. How interesting!

Tisha B'Av (the Ninth of Av) is an annual fast day in Judaism, named for the ninth day (Tisha) of the month of Av in the Hebrew calendar. The fast commemorates the destruction of both the First Temple and Second Temple in Jerusalem, which occurred about 655 years apart, but on the same Hebrew calendar date.

Is London is the "New Jerusalem" (Zion) ?
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It should be expected that there are people who will not be attending for religious reasons.
If not that, a fortunately scheduled dentist appointment and nagging wife will suffice for explanation later.