almost all my long distance rides are solitary, and a "latte lock" offers considerable peace of mind when stopped and away from the bike. Really worth the extra weight for the peace of mind they provide.

On my rides thru San Francisco and the like, an aluminum alloy U-Lock is fabulous deterrent, and very light.

The U-lock is hanging off the Brooks rails, between the seatpost and the Carradice. out of the way, ready to provide moderate security for heavily travelled stops or big cities. On a 300k permanent in coastal California or the east coast, i might even carry the alloy lock.