Whitechapel Bell Foundry has produced many a humdinger of a ringer in its 450 years of trading, including Big Ben, the Liberty Bell and (via a subcontractor) the current Olympic bell. The foundry on Whitechapel Road has long offered weekly pre-booked tours. During the Olympic period, however, it's open all day every day for anyone who wants a self-guided tour. You can take a snoop between now and 12 August between 10am and 5pm by simply turning up and handing over a tenner. The foundry contains a small museum, shop and education centre, as well as very friendly staff who are happy to talk about all things bell. Just don't let Jeremy Hunt anywhere near it.
Whitechapel Bell Foundry is at 34 Whitechapel Road. Image by M@. Thanks to Jo Cooper for the tip.