So in this lesson, it states 43% of fx transactions happen in London. But surely this means in the London session not just london correct?
I guess it means they are instigated through the London desks.
The capital involved is probably virtual anyway: it cannot be a stack of banknotes in storage at some geographical location. Keep in sight also that the banks deal in currency, but the majority of us (private retail forex traders) are not - we are betting on exchange rates.