Undoubtedly one of the city’s best tourist services, London Walks’ tour list is inspiring. On weekdays, there are often more than a dozen choices, and on weekends, nearly 25, which means that if you ever find yourself with a few hours to kill, you can always find instant occupation. Every tour (most are £10) departs from a Tube stop, and none require reservations, which makes arrangements easy. The marquee tour is probably “Jack the Ripper Haunts,” which heads out to the streets of Whitechapel around sunset and, in the pursuit of ghoulish entertainment, employs considerably more grotesquerie than uncontested facts. Many of the group’s other walks are more informative, including “The Blitz,” “Old Mayfair,” Harry Potter filming sites, and even guided tours of the British Museum. Other topics can supply authoritative tours on lesser-visited areas such as Hampstead village or the “Little Venice” near Regent’s Canal, places few other touring companies touch. The group also provides guidance (and discounts) for Westminster Abbey, as well as “Great Escapes!” of Bath, Stonehenge, Cambridge, Canterbury, and other day-trip favorites (entry fees and train transit are included in the price, £22– £53); they may go weekly or seasonally. If there’s any fault with London Walks, it’s that some groups swell to untenable sizes, and many of the guides, although proven knowledgeable when pressed, rely too commonly on canned performance shtick (in fact, many are actors, but then again, histrionics are preferable to a narcotic delivery). The best way to remedy both problems is to pick a tour with narrower appeal; you’ll have a better chance to ask questions. Tours are 2 hr.; prices and locations vary.