If your bike is locked outside the Curzon Soho right now

use a chain....as in a drivetrain chain looped around a seat stay and a rail...it's what "messengers" in NYC do, therefore it is cool, therefore do it!

con: makes your bike a little heavier and scratches your paint....seatstay pads anyone?

Just run the chain through an old length of inner tube - it'll stop it from scratching the paint and it'll also make it quieter.