“Provided that any mortgage or charge granted or created by a limited company on the whole or any part of its uncalled capital, whether before or after the passing of any such special resolution, shall have the same validity, force, and effect as if no such special resolution had been passed, save that, in the case of a mortgage or charge granted or created after the passing of such special resolution, the right of any person entitled by virtue of such mortgage or charge to require the calling-up of any uncalled capital affected by such special resolution shall be deferred until the event of the company being wound up.”