On 23 November 2013, the world marks 'The Day of the Doctor' — the Dr Who episode bearing that title and celebrating the fiftieth anniversary of the BBC television series will be broadcast simultaneously across the globe.

The time lord known only (so far) as 'The Doctor' hit British TV screens in 1963, the day after the assassination of US President John F. Kennedy. In 790 instalments since then he has battled daleks and cybermen, roaming through space and time in the TARDIS (from the outside, a 1960s London police box, although it's bigger on the inside) and 'regenerating' at intervals, such that the character has now been played by 12 actors — from William Hartnell to Peter Capaldi, who takes over the role next month.

The popularity of the series is such that it is now regularly broadcast in 50 countries, and the anniversary episode will be carried by TV networks in 75 countries. More than 200 cinemas in the UK, 30 in Germany and 50 in Russia will screen the episode in 3D, plus 100 cinemas in Australia and New Zealand (although on 24 November). For BBC Worldwide, the commercial arm of the public broadcaster, Dr Who is one of its biggest brands: a down-turn in revenues for 2012–2013 is attributed, at least in part, to the production in that time-frame of fewer Dr Who adventures.

So let the celebrations begin — grab your sonic screwdriver and join us behind the sofa...