Nearly all the experts Massei heard also said that a single attacker is totally possible, to explain the bruises and wounds, as well as the scenario.
I am not sure if CoulsdonUK is raising the issue of Meredith achieving an orange belt in martial arts... but these belts are awarded mainly to reward persistence, not necessarily merit. True, there can be some truly gifted martial artists who rise through the ranks, but that belt is the third level, ad only the second level that has much merit associated with it.
The first few years that I've seen of this training, is to train how to flee... not how to fight. The first few years also concentrate on how to fall, so that a rapid return to one's feet is possible... usually this involves hours and hours of rolls, all with the purpose of making sure the soles of one's feet are on the mat.
My own experience is that it takes until the blue or brown level when this becomes instinctual. During a mixed belt tournament, I remember clearly the first time a kid was knocked over - totally without thinking he rolled, placed his feet properly and sprung up to a standing position. He was a brown belt IIRC.
The discipline I have seen the most leaves the "disarming of an attacker with a knife," to the senior black belts. And even those are in well structured simulations with a rubber knife. Still, they are a sight to behold! I love the bit where the defender politely returns the knife to the attacker as if saying, "Let's do that again!"
So, CoulsdonUK, you may not have been raising this issue. I'm afraid it is simply not arguable, though - an orange belt would have been no match for a reasonably athletic person with a knife. Especially someone who also had a weight advantage in a fairly restricted space. "Restraining" the victim would not have been an issue for a single attacker.... with a knife. The are few, if any "experts" you see this as an issue in this case....