The October 11 announcement by British foreign office minister Hugo Swire instructing his high commissioner to go to Ahmedabad and meet with Modi is the culmination of a year-long process of closed-door meetings among BJP supporters in Britain, British and Indian business leaders, senior ministers and British MPs, particularly those with large Gujarati Hindu constituents from areas such as Leicester.
"This was a process, not an event," said a key interlocutor.
Britain was always key to Modi's strategy for gaining greater acceptance beyond Asia: if economically vulnerable Britain fell, then Europe would follow suit and, finally, America would come around. The outcome would mean an end to his pariah status, without which his ambition to be Prime Minister looked unlikely.
It was London - under Tony Blair's Labour government - that fired the first salvo against Modi. The 2002 sectarian violence that killed mostly Muslims, including three Britons of Gujarati origin, was described by a British internal report as "pre-planned and carried out with the full support of the state government."
During a visit to Britain in 2003, Modi was beset by protests from human rights campaigners seeking justice for the families of the three Britons. And in 2005, he was forced to call off a visit after campaigners sought an arrest warrant at Marylebone Magistrates Court in London on grounds of crimes against humanity.
Sensing the ugly mood, Britain banned its officials and ministers from having any direct contact with Modi and, although business ties grew, European countries followed suit and the US slapped a travel ban, citing "violations of religious freedom".
None of this deterred supporters of Modi. Lobbyists - including second generation Indians from families with close links to the RSS - pushed for his rehabilitation by melding three interdependent constituencies: the 600,000 Gujarati Hindu community; the two main British political parties, Conservatives and Labour; and British business leaders.
The move gathered momentum a year ago, just around the time Modi began to be projected as a possible prime ministerial candidate.
"The time is right for the UK to re-engage on the range of bilateral issues, not only for relations with India but also for the Gujarati community here," said a former British cabinet minister, who was closely involved with the talks. "You have to engage directly, even with governments you do not like."
"Back in 2002, we were right in leading the way in Europe in discouraging contact with Modi. The main consideration (in the recent discussions) has been that of course we should be engaging at a senior and more active level." According to the former minister and others involved in the talks - none of whom want to be named - the discussions primarily involved senior ministers, MPs, foreign office officials and political lobbyists within both the political parties.
The main considerations appear to have been economic and political, although participants are divided on whether the ethnic Gujarati Hindu vote was a consideration. "It may have been, but not once was the issue mentioned in any of the meetings," said the former minister. "On the other hand, sensitivity to the families of the British victims was a huge consideration."
Modi supporters in a powerful lobby called the Labour Friends of India have a different view. They point to a study by Conservative strategists that lists up to 40 constituencies where Indian voters hold the balance in deciding election outcomes. Many of them are Gujarati Hindus, they say. "It is important to note that this move had the support of both parties," said one member.
"The decision to re-open contact at a high level is political, not economic," said an Indian industry lobbyist. "The UK doesn't want to be seen as a country that doesn't protect the rights of its minorities. But there is also the realisation that you cannot have a special relationship (a term coined by Prime Minister David Cameron) with a country and not have relations with a man who could be its future leader."
Trading and global competitiveness, nevertheless, factor heavily in a country that is in the midst of a double-dip recession. British companies present in Gujarat include British Gas, Shell, Mott McDonald, British Petroleum, D&H Engineering, HR Wallingford, Reckitt & Benckiser, BMT India, Asite Solutions, MSBC Solutions, QX Solutions, Asian Media Group and others.
But the Americans outstrip the British when it comes to foreign direct investment into Gujarat. Between 2000 and 2010, British FDI going into the Reserve Bank of India office in Ahmedabad accounted for 5.47% of total UK FDI into India, compared to 12.4% of US FDI.
What appears to be more important in trading calculations is the reverse flow. There has been a steady stream of inward investment from Gujarat to the UK, including companies in pharmaceuticals, engineering and IT. One company has moved a number of its staff, including its CEO, from Rajkot to the town of Derby in order to provide software designs to Rolls Royce.
The fear among rights campaigners in Britain is that political and economic considerations may undermine attempts to secure justice for the families of the three British victims of the Gujarat riots - brothers Sakil and Saeed Dawood and their childhood friend Mohammad Aswat. The families have had to visit the crime scene themselves to find vital clues and collate forensic evidence, including the charred remains of bodies.
Minister Swire says the new policy of "active engagement" will not compromise on efforts to seek justice for the families. But Yusuf Dawood, brother of Sakil and Saeed, likens the move to former Prime Minister Tony Blair's controversial appeasement of Libyan strongman Muammar Gaddafi. "And we all know how that ended," he said.
"We still think he is the Butcher of Gujarat - he is yet to apologise for 2002," said Shamsuddin Agha of the Indian Muslim Federation. But prominent British Muslim peer and businessman Lord Adam Patel, who was very vocal in the anti-Modi campaign, now takes a surprisingly moderate view. "There is nothing wrong in meeting Modi. In fact, the discussions may lead to getting justice for the victims' families," he said.