Our grey world does not exist except in the imagination of the blue people. A startling statement, perhaps, but to those who heard the first two instalments of Laurence Marks and Maurice Gran's My Blue Heaven trilogy the concept should be familiar. To all others, welcome to the Douglas Adams-esque world of Graham Slater (Stephen Mangan), who is employed by his childhood imaginary friend, Mr Fluffy, a blue creature now known as Lapis Lazuli. He has to rid his friend's dimension of poisonous cash from the toxic debts that caused the global recession. Keeping up? Good, because this is brilliant stuff, full of neat wordplay and wonderful characters: Graham's indomitable mother (Phyllida Law) and her improbable stories; the child-like Mr Fluffy; and the steely, honey-voiced tax officer. Top marks (and Gran, too).