One evening in late November 2008, 10 gunmen arrived into Mumbai port in rubber dinghies. Within minutes, they had launched deadly attacks at six locations across the city, including the landmark Chhatrapati Shivaji Maharaj railway station and the Taj Mahal Palace hotel. When the attacks finally ended three days later, more than 160 people had been killed and India was left deeply traumatised.
A decade on, the wounds are still raw. On Monday, the anniversary of the attacks, politicians laid wreaths at a memorial in the city with Indian prime minister Narendra Modi leading tributes, writing that "a grateful nation bows to our brave police".
Part of the reason why the wounds still run deep is that the masterminds of the attacks have not been brought to justice. Nine of the 10 attackers died in Mumbai; the only surviving gunman, Mohammad Qasab, was sentenced to death for murder and waging war on India and hanged in Pune in November 2012.
But those who conceived the attacks have never faced trial. India almost immediately blamed the Pakistan-based militant group Lashkar-e-Taiba, which has links to Al Qaeda and is deemed a foreign terrorist organisation by the US administration, among others. Pakistan's government has never admitted responsibility – although when the ousted prime minister Nawaz Sharif criticised officials earlier this year for failures in the investigation, saying: "Militant organisations are active. Call them non-state actors, should we allow them to cross the border and kill 150 people in Mumbai? Why can't we complete the trial?" – Indian authorities were quick to interpret his comments as an admission of responsibility.
Relations between the two countries had reached stalemate when Imran Khan was elected as Pakistan's prime minister in July, on the back of promises to bring the perpetrators to justice. "All these years we have had a relationship which was detrimental to the entire subcontinent," he said in 2012. "We moved one step forward, two steps backward. Mumbai came [and] we were back to square one."
His accession to power heralded the promise of change and a chance, finally, for answers. But to do so, Mr Khan will have to tackle populist conservative forces and the shadowy influence of the army. If he can manage that, he will do more than resolve a 10-year-old question; he might finally be able to shake off the shackles of two of the strongest political forces in modern Pakistan.
But that vow to seek justice was made six years ago, before the likelihood of a former cricket star who had never held political office becoming prime minister. As the elections edged closer, Mr Khan appeared more comfortable courting some of the supporters of those accused of orchestrating the attacks.
In the aftermath of the 60-hour siege in 2008, Pakistan investigated and subsequently arrested two senior leaders of Lashkar-e-Taiba, Zaki ur Rehman Lakhvi and Hafiz Saeed. Lakhvi, thought to be the commander-in-chief of the attacks, was originally arrested on terrorism charges but released on bail in 2015 and has since disappeared. Saeed has been repeatedly arrested but released owing to a lack of incriminating evidence, despite having a $10 million dollar bounty placed on his head by the US and being on India's most-wanted list. Meanwhile six other associates of Lakhvi – Abdul Wajid, Mazhar Iqbal, Hamad Amin Sadiq, Shahid Jamil Riaz, Jamil Ahmed and Younis Anjum – have yet to be brought to trial after a series of twists and turns in their case, including frequent change of judges and the murder of a prosecutor.
The difficulty is that Lashkar-e-Taiba, although banned as an organisation by Pakistan, still operates in the country and provides extensive and effective social services, such as schools and ambulances, through its charitable arm Jamaat-ud-Dawa. Further, despite increasing international pressure to take action against the militant group, not least from the US, a Pew Global Attitudes survey found 14 per cent of Pakistanis looked favourably on Lashkar-e-Taiba while the younger generation were more inclined to be empathetic to its ideology.
And far from keeping a low profile, Saeed has pushed into politics, helping to found a political party named Milli Muslim League. When that party was refused permission to field candidates in this summer's election, it fielded them under a different party name, although none of them were successful.
But how well political parties linked to groups such as Lashkar-e-Taiba do at the polls is not the most pertinent issue. What makes it so difficult for Mr Khan to move against them is a broader movement of Islamist groups into political life, and his relationship to them.
Earlier this month, when a Pakistan court overturned Asia Bibi's conviction for blasphemy, there were widespread protests against its ruling. The protests were led by several hardline groups, among them Lashkar-e-Taiba.
These protests were the first major test of Mr Khan as prime minister, a tug of war between popular Islamist groups and the power of the Pakistani state. Despite his initially tough approach – as thousands blocked roads, he warned protesters not to “test the patience of the state” – he backed down somewhat, with his party agreeing to stop Ms Bibi leaving the country, fuelling yet more protests.
For Mr Khan, who made his independence from external influences a key part of his appeal, that patriotism has been too narrowly defined, allowing conservative elements to dictate politics.
Having first courted conservative public opinion, his failure to rein in these groups has instead empowered them. They see in “people power” the ability to openly defy the state and its institutions.
Using populist causes or stoking fears around India's behaviour towards Pakistan, these hardliners gain immense support.
It is here that Mr Khan faces his toughest test. There are suggestions that groups like Lashkar-e-Taiba enjoy both popular support and backing from powerful generals in the military and intelligence services.
Were Mr Khan to move against these elements, by properly investigating links between the attackers and Lashkar-e-Taiba, he would anger two powerful constituencies, Islamists and the generals.
Yet doing so is important primarily for Pakistan itself. Not only would answers for the Mumbai attacks help its frayed relationship with India but the primary victims of the extremism that has taken succour from mass Islamist movements have been Pakistanis themselves, tens of thousands of whom have died in terror attacks inside the country.
The Mumbai attacks have left a lingering legacy. Mr Khan would have to take on powerful elements in his own country to offer real answers. But doing so would lay to rest the ghosts of the past and drag power in Pakistan away from the angry mobs and the barracks, and back to the democratic institutions of the country, where it belongs.