What is the best lock?

lpg unless your bike is some carbon fibre wonder bike, no thief is gonna bend no rim, nor are they gonna power tool it. i still reckon most theives are just kids with bolt cutters, they won't be bothered getting through 2 D-locks. This is, of course, asssuming you don't lock it overnight on kingsland road or something.

During the day and if I am stopping an hour or less I use one lock and lock it up somewhere where it can be seen, after dark I use two, and I never leave it out overnight