In tonight's thought experiment, we feature David Tennant starring in 'The Bells of St John' and try to work out how different that would be. Suddenly it's 2008, which is longer ago than it feels, and instantly we're full of Standard Def Mockney goodness, trying to work out who could possibly replace Celia Imrie. Could it be...? Only one person, surely? Meanwhile, there's gherkins, potential Wilfred Mott, gags from 'City of Death' and that old RTD/Moffat debate. Who could possibly win? There's only one way to find out... FIGHT!