If Ian Fleming has been denigrated as a mere thriller writer, John le Carré has suffered a subtly different fate. He is widely credited with having taken the ­traditional English spy thriller and raised it to the level of literary fiction: a medium in which serious issues could be addressed in a sophisticated way. The trouble is that, by that benchmark, he falls short, and by some distance.

The issues with which he has grappled could hardly be more serious: they concern not just the sort of Britain we want to live in, but the sort of world we want to live in. But his dissection of that world, particularly in recent novels, can scarcely be called sophisticated. The plotlines have a cartoonish simplicity, with Uncle Sam cast as the villain, Britain as the duplicitous stooge and multinational companies as the Devil incarnate.

To the millions who fell under the spell of the young le Carré — a true master of his ­genre, able to write brilliantly about the Cold War from the vantage point of someone who had worked for the British embassy in Germany — his decline into a tendentious propagandist has been a sorry spectacle.

From a writer once known for his fine phrase-making plop the sort of agitprop ­clichés you hear in sixth-form debating ­societies. The Constant Gardener, we are told, concerns “the evil dealings of one of the world’s most prestigious pharmaceutical companies”. It is painful to see such an ­intelligent man launching such wild haymakers at his enemies.