There's a hulking great cathedral in the middle of the City called St Paul's. You might have noticed it. Christopher Wren's dome-topped masterpiece is a symbol of London's endurance and, such is its iconic status, it even appears in our logo. That's how important it is.
A tour of the cathedral is recommended at any time. The Whispering Gallery, views from the crown, monuments to Nelson, Wellington and innumerable other worthies, and the sheer magnificence of the interior make it well worth the £15 entrance fee (cf. £25 to go up the Shard). You can, of course, visit for free for Eucharist, Evensong or any other public religious service. But there's now a third way to visit the cathedral: by taking a tour of the parts that are usually off-limits to visitors.
The so-called Triforium tour starts half-way up the main spiral staircase, taking in a U-shaped space around the south, west and north walls. Immediately, we're drawn to hundreds of carved fragments from the medieval St Paul's, which line one wall. It's not every tour that lets you touch the remnants of one of Europe's great vanished buildings. Opposite, the cathedral library, styled by our guide as "the best-smelling room in St Paul's", is populated with countless old volumes, busts of former clergy and, we spied, a copy of Private Eye mocking the cathedral's position during the recent Occupy protests.
After the library, the tour visits the precipitous self-supporting spiral staircase, as featured in the Harry Potter films and the Madness of King George, among others. Visitors also get the chance to look down into the nave from the west end of the cathedral. The final room, and the main highlight for most, is Wren's shed-sized model of the cathedral, which itself took several years to carve.
Triforium tours take place on Mondays, Tuesdays and Fridays for groups of five or more. They must be booked in advance and cost £20 per person (but the price also includes access to the rest of the cathedral). More details here.
See other Alternative Tours of London.