A unique guidebook: The city beckons WHAT Winston Churchill called "the vast mass of London" can be overwhelming. Help is at hand, in a new digital wonder-box released in time for the Olympics. "London: A City Through Time" is neither coffee-table book nor guide nor map, but a nearly endless fusion of all three in a digital application, or "app" - nearly 2,000 years in the life of one of the world's great cities. The core of the app is the London Encyclopaedia, an 1,100-page doorstop first published by Macmillan in 1983, with 5,500 detailed entries on buildings, places, events and people. Into this mass of data the producers have injected cross-references and geo-tags, films and sound clips, archival photographs and rare historical maps. Users keen on the Tudors can nip from the palace at Hampton Court to a 1560 map of Civitas Londinium, and learn about Thomas Cromwell against the music of madrigals. Elegant timelines and street maps trace the city's development, from the Anglo-Saxon settlement of Lundenwic to the protests of Occupy London (the encyclopedia's most recent entry). Beyond boasting rights to detailed knowledge of the mechanics of Tower Bridge, users can spend hours watching Pathé newsreels - of the Blitz, the coronation of Elizabeth II, the suffragettes" campaign, and much more. But it is the cartography that reaches its full potential in digital form: zoom in tightly on Charles Booth's famous 1889 map of poverty zones, or a Victorian taxonomy of pubs called "The Modern Plague of London." The app also includes 360-degree photographic panoramas of everything from Westminster Cathedral to views from the top of the Shard. As a book, it would have been a bit much. But on a screen the material invites dipping in. The ease of navigation is largely due to the handiwork of two veteran British film-makers, Patrick Uden and Richard Loncraine. "What's important is not that it be comprehensive, but idiosyncratic," Mr Uden says. What lies above ground as you wait in the tube at Camden Town? Who was Samuel Pepys? What say the bells of Shoreditch? Even diehard Londoners are destined to discover something new. London: A City Through Time. Heuristic Media. Apple iPad version to be released in early July, iPhone version thereafter; $13.99 and £9.99