I don't believe there is any way to know for certain since BRW was not tracking his movements with scientific precision. He is mostly making an estimate of the time as you see in many instances in this case. A pedantic analysis of his various statements are somewhat insightful but can never answer the question when he himself didn't really know. Most people don't go around noting the exact time of every mundane event in their life down to the minute.
I agree,
BRW's estimation of how long he spent on the 6th floor varies wildly.
He starts off by lying about not being on the 6th floor (or is he telling the truth?)
Once he admits he was on the 6th he gives the following estimations, in various statements, for how long he was up there - 3, 5, 10, 12, 15, 20 minutes. There is a pattern to these estimations - the more he is questioned, the longer he was up there.
Obviously, it isn't just a case of looking at what BRW has to say, there are other witnesses whose testimonies shed light on how long BRW was on the 6th floor.
But you know that already.
What's important is that BRW never suggested that he heard or saw anything unusual.
What's important is that he lied about going up to the 5th floor with Jarman and Norman (or did he lie about having his lunch alone on the 6th floor?)
What's more important is that after he has corrected his first statement, Jarman and Norman continue supporting the initial lie (if it was a lie) that BRW goes up to the 5th floor with Norman and Jarman. When it comes time for the WC hearing everyone seems to have got their stories straight. All now agree BRW went up to the 6th on his own then joined Jarman/Norman later.
Any narrative that has him encountering a hit team on the 6th floor and being allowed to go about his business perhaps raising the alarm is absurd. Instead he goes to the window just below where he knows this is going to happen and puts himself at further risk? Not plausible.
Agreed.
How can BRW be allowed to just wander off. The assassin must "neutralise" him in some way - tying him up or even killing him. He can't set him free hoping he won't raise the alarm just because he "promised".
My interpretation of various statements has BRW on the 6th floor less than five minutes before the arrival of the motorcade and there is some evidence he was actually in the SN having his lunch.
In this scenario 3 possibilities exists:
The assassin(s) have yet to arrive on the 6th floor so BRW is alone until he goes down to the 5th.
The assassin(s) are on the 6th floor but BRW is unaware of it.
BRW is aware someone is on the 6th when he goes down to the 5th.
All three scenarios are problematic in different ways.
This is where the historic piece of chicken comes into it. For his lunch BRW has a piece of chicken, two slices of bread, a bag of Fritos and a bottle of soda pop. He strips some off the chicken and makes a chicken sandwich, has his Fritos and pop, saving the big lump of chicken remaining on the bone to finish off. Remember, he's been working hard all morning and will be doing the same in the afternoon and his piece of chicken is his main nourishment for the day. So, what are the chances of him just wandering off, leaving the main part of his lunch behind? Surely, the partially eaten piece of chicken indicates BRW was interrupted before he got to his chicken and left in a hurry.
If he was confronted by a stranger/stranger with a rifle/familiar face with a rifle Williams would surely have raised the alarm - he certainly wouldn't have gone down a floor to carry on watching the motorcade.
However, if he was confronted by a familiar face, without a rifle, who just told him to f%&k off immediately, there would be no reason to flee or panic. But when the shots started ringing out from directly above them BRW puts two and two together. He has just seen the assassin, what should he do?