Rivendell Sam Hillborne, Brompton S/M3L (modified)
Two locks for sure. If I am going to a high risk area, I bring two Kryptonite U locks and I have my seat chained to the seat stay. It is heavy but worth it. Less risky areas I just bring one Kryptonite and one Krypto cable. At work, even with a locked bike compound and video surveillance, I still use three Kryptonite U locks and one cable but I leave the locks there so I don't carry the weight. Again I work in a high risk bike theft area.
In total I have 7 Kryptonite U locks and four Krypto cables to lock my bikes. Even in my apartment building I use 2 U locks per bike plus a cable. I did try the New York Chain lock by Kryptonite but I found it heavy and scratches the frame because the sleeve around the chain is not long enough so I sold it. When I buy a new lock that I don't have to carry I will get the Kryptonite New York Series U lock.
Like you my bike is probably the best bike to steal at work but I am hoping when they see the number of locks they have to cut, they will move on to the next easier target. One thing I don't do is I never leave my bike outside overnight.
If I am just running into a store I use a mini Kyrptonite U lock and one small Krypto cable.