No I haven't - at times Speedway, for some reason does go in to decline. However there is no way you can say that the GPs have slowed or reversed the decline. What they have done is to be, to a large extent, responsible for the really TOP Riders not racing here in Great Britain any more. As the top Riders have left, so crowds have dropped - it isn't rocket science. Now we are down to the hard core older demographic Supporters, like myself, who will continue to support the Sport until they 'die off'. With very few young Supporters coming along - Speedway will eventually do the same in this Country.
So there you are - you are working from a false premise.