When Dame Lowell Goddard resigned as head of the Independent Inquiry into Institutional Child Sexual Abuse at the start of August, it was clear that the whole story was yet to come out – not least because her resignation letter simply read:

“I regret to advise that I am offering you my resignation as Chair of the Independent Inquiry into Institutional Child Sexual Abuse, with immediate effect. I trust you will accept this decision.”

Today we learn rather more about exactly why she decided to leave the job – in short, because she thinks the inquiry’s scope is too broad, and its resources too limited. A leaked memo from Goddard says:

“With the benefit of hindsight, or more realistically the benefit of experience, it is clear there is an inherent problem in the sheer scale and size of the inquiry (which its budget does not match) and therefore in its manageability.

“Its boundless compass, including as it does every state and non-state institution as well as relevant institutional contexts, coupled with the absence of any built-in time parameters, does not fit comfortably or practically within the single inquiry model in which it currently resides…”

“…I have recommended in my report to the home secretary that my departure provides a timely opportunity to undertake a complete review of the inquiry in its present form, with a view to remodelling it and recalibrating its emphasis more towards current events and thus focusing major attention on the present and future protection of children.”

This poses a tricky challenge for Amber Rudd. The inquiry was hailed, particularly by victims’ groups, as an opportunity to look under every stone and explore the facts relating to every institution which faces allegations of child abuse stretching back decades. However, it is also clearly intended to be more than a retrospective truth commission – it is also meant to improve the protection of children now and in the future.

If, as Goddard implies, those two duties are coming into conflict – the sheer scale of the retrospective investigation threatening to make it impossible to produce practical benefits for modern-day children – then one will have to win out.

That wouldn’t mean ditching all retrospective investigation, obviously. Looking at what has gone wrong in the past is essential to improving things in the future. But Goddard seems pretty clear that scrutinising all institutions with no time limit is unsustainable.

Any limits will inevitably and understandably attract criticism from some of those affected, and less reasonably from the conspiracy theorists who follow this topic like birds following the plough, which won’t be an appealing prospect for the Home Secretary. It will be a tough choice, but to make the inquiry viable she may yet have to redraw its boundaries.