Just a note, Carradice makes a Nelson saddlebag and the larger Camper saddlebag, both also come in a "longflap" version which is useful as it gives the option to greatly expand the volume if you need to carry something extra. I use a Camper Longflap and will often deploy the longflap to carry food/beer from a market to a campsite.
Yes. I got my model naming a bit mixed up there. It's the Carradice Nelson/Nelson Longflap and the Carradice Camper/Camper Longflap. I have the Nelson Longflap, and it is terrible useful for expanding to take extra stuff. And it is amazingly waterproof... enough so, that I wouldn't hesitate to keep electronic stuff in there.