Graham, I think you are probably right but how would he create that effect with the float being allowed to go downstream of the fish.Where would the pull effect come from?
I've tried the pulling fish into a snag to get it to swim the other way and guess what I pulled them into the snag.This was also on the Swale John, at Cundall Hall, where you would hook the barbel about 10 yards downstream and all they would do was swim towards you very steadily before diving into a willow just upstream at a rate of knots.The only way you get them out was by sinking the rod tip to below the level of the branches in the hope the float would not get caught up.
I've never known Barbel fight as much as those Swale fish.
I'd always prefer to play a big fish upstream om the float.If you are clever you can release the pressure at the right point and it will drop with the current into the net.Barbel some times can be coaxed upstream but big chub are a much more difficult as they have a tendency to just come to the surface on a long downstream line with their mouths open and its like playing a plastic bag.Often the hookhold gives with the pressure of current.Never really come up with a way of countering this apart from going to meet the fish if the bank permits.