Carradice Pendle. But I am no Randonneur. Commuter and recreational rider.
Fits lotsa stuff. Has slots on the lid for adding longer straps to strap stuff to the outside of the bag (not pictured).
I keep a rain poncho, splats, couple tubes, pump, tools, wallet, iPhone, flat kit, etc., and still have space for lunch.
https://www.flickr.com/photos/702377...7633085407086/
https://www.flickr.com/photos/702377...7633085407086/
rivbike.com sells huge saddle bags of another brand.
Carradice has much bigger models, too.