Ok so the thing is this 96 minute window, all these things had to have happened, based on Prime Suspects post (sorry cannot link it as old thread)
WT had a fatal accident within minutes of the photo taken,
FM hid the body immediately (presumably in FGM car or temporarily in roof cavity/under house???),
FM made 2 landline phone calls, one to BS about washing machine, 2nd call to GO about the deck,
not having cups of tea and catch with her mother but plotting what to do next,
decided to 'look' for WT,
transferred body to FGM car or the body was already in boot after immediately after accident,
disposes of body by burying in the bushes while 'searching' for WT.
FGM has agreed to last sighting of WT outside playing,
FM calls FF on phone and he's taken it on board, and is instantly agreeable to a cover up.

FF returns home and the whole charade begins.
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Ok things that do not add up to me is the ability for all this to happen and a covered up in the 96 minutes. Not to mention it would be the FM dictating that it be 96minutes. Remember she chose to call the police at that time, why not giver herself more time, why not a whole day. Was it done so the FF wouldnt find out, seems odd.
Also people are not career criminals, I assume anyone here would think that when a kid goes missing that LE would check attics and basements and sniffer dogs in car boots etc. We see so many crime shows we would just know we wouldn't get away with it or wouldnt think we would. The FF would be the same. It seems like an extremely high risk for little reward, if accident theory is correct, the risk of being caught with a dead body in the attic (or wherever it was) is a lot more than getting charged for a tragic accident.
Im starting to think that they have gone over every single bit of information and they have absolutely no one they can get a solid case on, and they only thing that has not been thoroughly checked it seems is the FM and the car/house. Also they are basing the entire investigation on the first statements of the FF, so maybe now the tactic is fresh eyes, lets look at it as though those statements are false and see where we end up. Honestly this should have been done at the beginning, and according to the FF they invite any thorough investigation, so I hope they still stand by this.
The AVO and the assault charge, whilst serious, it could be a trumped up charge to scare them and see if they break, the police may know full well it wont lead to anything (want to stipulate I have no more info than anyone else, it could be a very serious abuse incident). But we dont know anything about the circumstances, was this a child who went to their teacher to say abuse occured, were police called to an altercation. Or did someone see bruising and didnt believe the story told by the daughter and/or foster family.
Its such a tight window, and unless the accident occurred because of temper or anger or premeditated its seems strange that it would be covered up. Also not just getting your daughter and elderly mother to play along, but play along convincingly. Thats what gets me they would all have to be so convincing. Unless the mother knew the police would blame the Bio family, and led them down that path. But again, such a tight window to even calm done enough to convincingly pull it off.