A short proof of the result on actions that characterize l∞n Original Research Article

It is well known that, if the identity operator on an n-dimensional Banach space V can be extended to any Banach space with the same norm, then V is isometric to l∞n. We give a short proof of the result due to B. Chalmers and B. Shekhtman (Linear Algebra and its Applications 270 (1998) 155–169) saying that the identity is (in some sense) the only such operator.