A wave of bitter collective grief is beginning to break across the land of the stiff upper lip. You can sense it every time another funeral cortège wends through Wootton Bassett. You could feel in the subdued crowd that packed Whitehall on Sunday.

You can see it in the tired eyes not just of the newly bereaved widow and her frightened children, but also of those turning out in their support, and of those writing and reporting on it. Mourning is exhausting.

This upsurge of public grief has not happened simply because Remembrance Day coincided with a savage rise in the death toll in Afghanistan. It does not merely reflect ebbing support for the war, anger over our political leaders, or uncertainty about our war aims.

It feels more elemental than that — a deep-tissue communal sadness, a sense of shared hopelessness that comes with the tragedy of sudden, violent death. This collective grieving happens quite rarely in British society, but when it does, its effects — social, cultural and, above all, political — can be profound.

Traditionally, Britons have disdained exhibitions of public emotion, particularly in wartime. Mass demonstrations of bereavement, whether for famous individuals, family or war dead, were seen as a sign of weakness. An entire empire was built on the ability to suppress emotion.

During and after the First World War, excessive public grieving was forbidden, bequeathing a poisonous legacy of unaddressed trauma. That war left about three million widows and six million orphans, but public anguish and protracted mourning were seen as unpatriotic.

An entire generation of combatants was encouraged to cauterise the wounds of memory. The response to the question “What did you do in the Great War, Daddy?” was usually a gruff refusal to discuss it. Real grief was subsumed in the official trappings of heroic death: war memorials, statues, Kipling’s restrained epitaphs and euphemism. The emotional reality of war was stifled.

The Second World War also discouraged the wearing of hearts on sleeves, particularly uniformed sleeves. The culture conspired to suppress overt mourning: if Noël Coward could show no emotion amid the carnage in In Which We Serve, so should everyone else. Grief was just collateral damage. “Keep buggering on,” Winston Churchill ordered.

The turning point came with the death of Diana, Princess of Wales, which prompted an expression of mass grief unequalled in British history. Before her death the ability to suppress emotion was regarded as a virtue, restrained mourning a mark of decorum: exactly the qualities for which the Royal Family were pilloried. The grieving may have been extreme and exacerbated by crowd mentality, but it was undeniably authentic. The way we mourn changed for ever: today it is not only reasonable but cathartic publicly to mourn someone you have never met.

Some dismiss the Diana effect as banal and meaningless, a “new emotionalism” that allows strangers to wallow in mawkish sentimentality and piggy-back on the genuine bereavements of others. Some see the growth of public grieving for dead celebrities and murdered children as “mourning sickness”, driven less by real emotion than by the desire to be seen to care.

Mourning was once the preserve of the elderly. Today’s public mourners are far younger, brought up in an atmosphere of emotional honesty and openness to collective grief. The crowds in Whitehall and yesterday in Trafalgar Square contain many of the Facebook generation, come to remember the dead of their own age after eight years of war.

Gordon Brown comes from a generation where mourning is private, but to demonstrate sympathy for the bereaved he has had to evoke the death of his own daughter.

Grief is not easily put into words. It is more simply represented by ritual, wreath laying and hymn singing, flowers, candles, prayers and two minutes of silence. But at a more profound level, mourning can simply mean turning up to stand with others similarly distressed.

This is what is happening, with increasing intensity at Wootton Bassett and throughout the country. There is solace in solidarity and comfort in crowds. And the crowds are growing. Most of the 2,000 people who turned out this week did not know the dead soldiers personally. This public mourning began spontaneously simply because the route from RAF Lyneham passes through the Wiltshire town, and has grown organically.

There is a medieval pilgrimage gene in our national make-up, and once again we are gathering to mourn. The Wootton Bassett crowds are primarily emotional, but are steadily becoming more political, in protest against the Government and the policy in Afghanistan, just as mourning Diana became focused into resentment towards the Royal Family.

Public grief for the dead of the Afghan war can be sentimental and manufactured but, in an age when we no longer fear emotion, it demonstrates a willingness to confront the true nature of war and death in a way that our ancestors in two world wars too often did not.

In 1996 I attended the 80th anniversary of the Battle of the Somme and met a man called Donald Hodge, then 101, who had gone over the top on the first day of the carnage. While the top brass spoke of courage and sacrifice, 80 years later, Mr Hodge was still grieving. “I have so many friends who lie here,” he said. For someone of his generation to speak openly of his own grief was proof of a different sort of bravery.

A palpable sombreness hung over this year’s Remembrance Day ritual, a collective sense of loss. Perhaps that is war frustration or political disillusionment, but it also shows how far we have come in acknowledging the painful and bloody reality of war, when a lip trembling in shared grief is a greater badge of honour than a stiff upper lip.

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