I've made a few notes from the Observer podcast with Chloe H and her editor about when she contacted Raymoth.
It seems she did as soon as she had the initial tip off, which was not about the financial allegations, and she offered them an interview. Declined.
She then investigated and went back saying things she'd discovered didn't tally with what they'd said in the book and elsewhere. No response.
She waited "a couple of days " and wrote again, listing what she'd found out and again offering a meeting. Response from their lawyers saying that it was usual to give people a week especially with something so complex. The Observer offered a week and they then asked for more time. Chloe says they gave them as much as possible given the print deadline and they got the brief initial response about the "physical and emotional journey"
I hope this is accurate. What it says to me is that they knew this was coming and from an early stage.
ETA missing word