L ife on Earth has a good claim for the top spot in any list of the best British TV shows of all time. A giant leap forward from previous wildlife programmes, it gave us the David Attenborough epic as we now know it: every expansive, expensive, dazzlingly informative BBC nature series since has used a template that Life on Earth created. It’s a classic, a landmark, a totem of the creative power the Beeb once had. It’s now 50 years since it went into production, and it’s Attenborough’s 100th birthday this week. As TV anniversaries go, this is a weighty one. You might worry that a retrospective film about Life on Earth could be an hour of solemn awe and hushed reverence. What you actually get from Making Life on Earth: Attenborough’s Greatest Adventure is a relentlessly entertaining cavalcade of top-drawer anecdotes, more like the sort of gossipy celebration that might commemorate the making of Jaws or Star Wars.…