Hi Cawky
The crowd will be governed by what the weather turns out to be like, after all there is no cover at all alongside the river.
Looking on the bright side, no rain, I would anticipate something in the region of 100,000 onlookers. If it is raining then I would expect perhaps 20,000.
Of course it always makes me wonder how the "powers to be" actually come up with the numbers attending these events, especially when the spectators will be so spread out?
Regards
Steve Ellwood