Britain’s commemoration of the Great War has lost all sense of proportion. It has become a media theme park, an indigestible cross between Downton Abbey and a horror movie. I cannot walk down the street or turn on the television without being bombarded by Great War diaries, poems, scrapbooks and songs. The BBC has gone war mad. We have Great War plays, Great War proms, Great War bake-ins, Great War gardens, even Great War Countryfile. There is the Great War and the Commonwealth, the Great War and feminism, Great War fashion shows and souvenirs. There are reportedly 8,000 books on the war in print. The Royal Mail has issued “classic, prestige and presentation” packs on the war that “enable you to enjoy both the stories and the stamps”. Enjoy?

Meanwhile our finest historians compete to find the most ghoulish tales from the trenches, the most ghastly cruelties, the goriest wounds. No programme appears on television without some footage of men running through mud. Is there no other way of remembering an event than with images of death, punctuated by men in top hats with silly walks?

This has been going on all year. When in January I apologised to German friends for the impending avalanche of anti-German memorabilia, I little realised how great that avalanche would be. A Martian might think Britain was a country of demented warmongers, not able to get through a day without a dose of appalling battle scenes from past national victories. On Monday the fact that Britain went to war with Germany in 1914 actually led the morning news. Was this on government instruction? Were this North Korea or Maoist China we would ridicule such craven chauvinism.

Clearly events of the magnitude of a war should be remembered. But when those who fought and suffered are almost all dead, “remembering” is a task for the intellect and imagination. It is essentially work for historians, but we have to pump up “human interest” in it, especially for children, with tales of personal distress and terrible cruelty. The repetition of virtually identical “stories from the trenches” becomes banal, a nightly pornography of violence.

The war was terrible, as are all wars. As the historian Max Hastings remarked on Radio 4’s Today programme , the soldiers who experienced Napoleon’s march on Moscow or the Russian front in the second world war would have regarded the trenches as easy going. Besides, the actual outbreak of a war is by no means its most significant moment, which surely attaches to its completion. No one in 1914 thought they were marching off to “the Great War”, but rather to drive the Germans back over their border by Christmas.

Needless to say, the centenary has been seized as a military propaganda opportunity. Last week David Cameron crudely compared Vladimir Putin in Ukraine to Germany under the Kaiser in 1914 (and under Hitler). This was neither true nor helpful. The prime minister added that Britain was “not about to launch a European war”. In which case why mention it at all, and why also send troops to train in eastern Europe?

Eagerly jumping on the rolling bandwagon was the chief of the general staff, Sir Peter Wall. In the Telegraph on Monday he added that recent wars had bred a “warrior generation” of soldiers eager to take the fight to any available enemy – even back to Afghanistan, of all places.

The most sensible commemoration of any war is not to repeat it. Hence, presumably, the constant references by this week’s celebrants to “drawing lessons” and “lest we forget”. But this is mere cliche if no lessons are then drawn, or if drawn are then forgotten.

The Great War centenary should indeed have been a festival of lessons. Historians have had a field day arguing over its enduring puzzle – not its conduct or its outcome, but its cause. I have come close to changing my mind with each book I have read, veering from Chris Clark’s cobweb of treaties and tripwires to the majority view that firmly blames the Kaiser and Germany. But I have read precious few lessons.

The truth is that Britain is as bad as America at learning from old wars. The American defence secretary during Vietnam, Robert McNamara, remarked that every lesson of Vietnam was ignored by the invasion of Iraq. In the past decade Britain has waged three unprovoked wars – on Afghanistan, Iraq and Libya – at a vast cost in lives and destruction, and no obvious benefit to anyone. The invasion of Afghanistan ignored the lesson of all previous conflicts in the region and is duly being lost. The truth is that “drawing lessons” has become code for celebrating victory.

I doubt if any lessons will be drawn next year from the anniversaries of Agincourt (1415) or Waterloo (1815) – and certainly none from the Battle of New Orleans (1815). We will just ring bells, bake cakes and put on costumes.

Nor is the Great War celebration over. There are still four years of fighting to go, from the Marne to the Somme to Passchendaele to Amiens. We can have “Oh! What a Lovely War” each evening. Someone at the BBC will perhaps try to replay the Anglo-German football match in no man’s land – and try not to win. And what of Armistice Day? We know where that will lead, to the classic British 20th century Boche-bashing.

The chief lesson of 1914 must be not recklessly to rattle sabres across the frontiers of Europe until all else is lost. The Germans have learned that. In Ukraine they are still counselling restraint. Britain is doing the opposite, as its leaders gently dust themselves in glory. When Cameron last year allotted £50m to “remembering the lessons” of 1914, he was also planning to go to war on Syria. I wonder what lesson taught him that.