Keith Vaz described the letter he received from the most senior official at the Home Office – just days ago – as one of the best he had ever seen.
The chair of the Home Affairs select committee was particularly impressed by the level of detail provided by Mark Sedwill.
He was surprised about how frank the permanent secretary had been about a Home Office investigation into its own handling of historical child sex allegations against politicians.
The letter recounted how hundreds of files were raked through, with correspondence passed to the police.
It said a single overarching dossier, said to be compiled by the late Tory MP Geoffrey Dickens, was never found.
But the key admission was that 114 “potentially relevant” documents had got lost, gone missing or been destroyed.
Despite that the Home Office investigation, which took place last year, concluded that officials had done nothing wrong – implying that the destruction of the documents was simple protocol.
Yet campaigners and lawyers representing potential victims jumped on the revelation – warning that the missing files may have contained crucial evidence that could lead to convictions.
Acknowledging public distrust over the issue, Mr Sedwill promised to bring in an independent legal expert to review last year’s investigation.
On Tuesday, the permanent secretary will appear before the select committee – his first public appearance since the letter was released.
He is likely to name a QC and set out the terms of reference for the review.
But he is also likely to face questions from MPs about the lost documents.
Suspicious MPs will want to interrogate him about how the Home Office could say the original allegations were properly dealt with when so much potential evidence was missing.
Simon Danzcuk – an MP who has been campaigning for alleged victims – says the department is guilty of either incompetence or a cover up.
He – and a growing number of MPs (now over 140) – want a full “Hillsborough”-style public inquiry.
They say an internal review can’t possibly get to the bottom of this.
Instead they want a process that can see former home secretaries and officials questioned – including those who saw the original files.
Downing Street is resisting such a move – saying an internal review is the right approach.
A source said the allegations of victims should be scrutinised by the police not Government.
They have support from David Mellor who was a Home Office minister at the time the dossier was compiled.
He describes Mr Dickens as a “rent-a-quote” MP and suggests the dossier is a weaker document than has been suggested.
He thinks claims of a Westminster paedophile ring are exaggerated.
But a Conservative colleague who sat in Margaret Thatcher’s cabinet – Lord Tebbit – takes a different view.
He says there was an instinct in the 1980s to protect the establishment.
With such a senior figure suggesting that a cover-up might have been possible – the questions of critics are unlikely to go away any time soon.