The Hinduja file is reopened over lunch in New Delhi

The Hinduja scandal is the closest the Labour party has to radioactive waste. Though officially buried five years ago, it remains lethal: the Indian billionaires had involved so many powerful people in their quest for British passports that the scandal threatened to engulf the whole government. In the event Peter Mandelson was — conveniently for New Labour — the only casualty of the affair. His downfall was so spectacular, and so gleefully received, that little attention was paid to the subtle, sometimes playful clues Sir Anthony Hammond left in his official report of March 2001, pointing those who cared to look towards a much deeper mystery.

The former Treasury solicitor turned Whitehall gumshoe disclosed without comment the astonishing influence which the Hindujas commanded at the highest reaches of government and how they lobbied for passports while discussing their contribution to the Millennium Dome. But Hammond’s findings suggested an intimacy between New Labour and the brothers that could not be explained by a single donation. Hammond tells us how Jack Straw, then home secretary, processed a memo asking about a passport for Prakash, the youngest brother, and scribbled on it ‘Zola Budd’, a reference to the South African athlete whose British passport was approved in ten days. Cabinet members spoke to junior ministers and private secretaries as if they should know who the Hindujas were, as if it were gauche to ask. So the real question — unanswered to this day — was how the brothers came to hold New Labour in such thrall.

Read again today, as the Metropolitan Police is investigating whether Labour sold honours, and the Home Office is in meltdown, the Hammond inquiry looks less like a whitewash and more like a terrible prophecy. Yet we still have no explanation for the Hindujas’ hold over Labour, especially as the brothers insist they gave nothing to the Labour party itself.