In a dramatic illustration of his attempt to place Anglo-Indian relations on a new footing, he will become the first serving British prime minister to visit the scene where at least 379 Indians lost their lives. Cameron, who regards the killings as one of the most deeply shameful events in British colonial history, will lay a wreath in their memory.
The massacre emboldened the Indian independence movement and helped end the British Raj 28 years later in 1947. The Indian National Congress estimated that the death toll, after Brigadier-General Reginald Dyer ordered his troops to open fire on a crowd in Amritsar in April 1919, was closer to 1,000.
Cameron on Tuesday night acknowledged the significance of his pubic act of remorse. He said: "There are ties of history [between UK and India] – both the good and the bad. In Amritsar, I want to take the opportunity to pay my respects at Jallianwala Bagh."
The gesture by Cameron, which comes 16 years after the Queen paid her respects at the Jallianwala Bagh public gardens during a state visit to India, will be the most serious attempt by Britain to make amends for one of the most notorious episodes during the Raj. But Cameron will stop short of offering an apology for the massacre which was described the following year by Winston Churchill, then secretary of state for war, as "monstrous".
Government sources said Cameron believes it would be wrong to apologise for two reasons. It would set a precedent which could lead to endless demands for apologies for other events throughout British colonial history.
Cameron also believes the British state acknowledged the horror of the massacre at the time. Dyer was removed from his position and forced to retire the following March. The official report into the massacre, known as the Hunter commission, was highly critical of him.
One government source drew a distinction between the inquiries into Bloody Sunday in 1972, the policing on the day of the Hillsborough disaster in 1989 and the recent Mid Staffordshire NHS scandal which all prompted apologies from the prime minister. "In those three cases the state, or organs of the state, were at fault and so the prime minister apologised," one source said. Cameron believes that an agent of the state – Dyer – rather than the state itself was at fault in Amritsar.
Cameron was offered support on Tuesday night by the Bollywood actor Aamir Khan, who said there was no need to make an apology for mistakes during the Raj. Speaking after the pair met in Delhi, Khan said: "I don't think we can hold the present generation of Britishers responsible for something that happened ages ago. It is not fair."
Cameron acknowledges he will be taking a big step in Amritsar. He regards his public gesture as an important part of addressing painful memories from the past to allow Britain and India to focus on a closer trading relationship in the future.
But Cameron believes he is acting in line with Britain's response to the massacre dating back to its immediate aftermath. Edwin Montagu, then secretary of state for India, described Dyer's behaviour as an example of the "doctrine of terrorism".
Cameron points out that the Queen acknowledged the scale of the disaster in a speech on the eve of her visit to Amritsar. She said: "It is no secret that there have been some difficult episodes in our past. Jallianwala Bagh, which I shall visit tomorrow, is a distressing example. But history cannot be rewritten, however much we might sometimes wish otherwise. It has its moments of sadness as well as of gladness. We must learn from the sadness and build on the gladness."
Tony Blair visited the scene of the massacre before he became prime minister. He described it as the "worst aspects of colonialism".
As foreign secretary, Jack Straw wrote in the Jallianwala Bagh visitors' book in 2005: "This was a terrible occasion in which so many innocents were slaughtered: and for which I feel ashamed and full of sorrow."
Cameron, who has his eye on the Sikh vote in Britain, will also visit the Golden Temple in Amritsar, Sikhism's holiest site. He said: "Punjabis make an extraordinary contribution to British life and I'm delighted to have the chance to visit the land of their ancestors. There are ties of religion. Sikhism is one of the key faiths not just of India, but of Britain now too. And I cannot wait to see the Golden Temple in Amritsar, which I believe is one of the most beautiful and extraordinary places of worship in the world."
Massacrre that boosted Indian independence
The Amritsar massacre of 13 April 1919 crystallised the decline and eventual fall of the British Raj.
In the space of a few hours, Brigadier-General Reginald Dyer did more than any other person to end British rule in India, when he ordered 50 riflemen to open fire on thousands of innocent Indian protesters. At least 379 people were killed at the Jallianwala Bagh public garden, though the Indian National Congress placed the death toll nearer 1,000.
Dyer's actions, which were portrayed by Edward Fox in the 1982 Richard Attenborough film Gandhi, emboldened the Indian independence movement. Public revulsion at his actions played a decisive role in winning support for the lengthy campaign of peaceful civil disobedience led by Mahatma Gandhi which culminated in Indian independence in 1947.
But the elite of the British Raj did not see the massacre as an inevitable step towards independence, which was hastened after the second world war by Gandhi's campaign and by Britain's parlous public finances.
Britain believed that its response to the massacre was exemplary. Dyer was forced to retire a year later and a succession of political leaders denounced his actions.
Winston Churchill famously described the shootings as "monstrous". As secretary of state for war he told the House of Commons on 8 July 1920: "That is an episode which appears to me to be without precedent or parallel in the modern history of the British empire. It is an event of an entirely different order from any of those tragical occurrences which take place when troops are brought into collision with the civil population. It is an extraordinary event, a monstrous event, an event which stands in singular and sinister isolation."
In the same debate the secretary of state for India, Edwin Montagu issued a scathing response to Dyer's claim that he had not overreacted and that he would have called in even greater firepower: "That it is the doctrine of terrorism."
David Cameron has a link to the debate that was held on a technical motion to dock Montagu's salary. His great-grandfather, Sir William Mount, voted with Churchill and Montagu as MPs rejected calls to lower his salary.
guardian.co.uk © Guardian News and Media Limited 2010
image: © University Hospitals Birmingham