The history of Bordeaux en primeur

Following up my post on Madness in Bordeaux...

I hesitate to give a Bordelais negociant a history lesson, but when Patrick Bernard of Millesima suggests that 

"For over two centuries, the Bordeaux Grands Crus Classés sell their harvest en primeur, in springtime, to the Bordeaux Negociants."

I don't think he's being strictly accurate. The modern en primeur system (based on selling wine in barrel in the spring following the harvest), far from being 200 years old is actually roughly a quarter as old as that. Until the 1961 vintage, the chateaux mostly sold their wine sur souche - while it was still on the vine, prior to the harvest. It was the surprisingly small volume of that great vintage that shifted the transaction until after the grapes had been picked. There may have been some spring, post-harvest transactions, but I understand these to have been the exception to the rule, especially in days when the wine was routinely bottled by the negociants.

Maybe M Bernard would like us to return to the sur souche tradition. After all, it has much deeper foundations in Bordeaux history...