Samir, none of this is about when i saw you lose the lead or guessing anything. The video shows you having lost the lead at the point where you turn into Bennet Road from the roundabout. I know these streets. That is 0.42 miles from the start at the bus shelter on Longwater Avenue according to the OS 1:1250 mapping on my MapInfo software, which is about as accurate mapping as money can buy.
There's not rrally any wriggle room here. You had lost the lead by 0.42 miles. None of this really matters, but sometimes its nice to deal in hard facts.