The fringe separation in high-resolution electron microscopy images of carbon nanotubes changes from equally spaced on both sides of the tube hollow to unequally spaced and expanded on one side when tilted about the tube axis. This observation cannot be explained by the previously proposed equally spaced coaxial shell model. An unequally spaced non-coaxial closed shell nested model is proposed. Unlike the equally spaced imperfect shell model, there are no intrinsic defects and thus no dangling bonds associated with the unequally spaced closed perfect shell nested model. The recently reported compressive and intercalation behaviour of carbon nanotubes can be rationalized in terms of the unequal spacing and morphological defects in the nanotube structure.