Stairs with open side

Other

Hi

I've purchased a property for letting and the internal staircase has a bannister on the wall up one side but on the other it is open sided until two thirds of the way up. Am I right in thinking I cannot let it out with an open side of the stairs? Do I need to install some slats and/or a secure bannister up the open side?

I seem to think this is the case for safety reasons to avoid anyone falling off the side of the staircase and claiming against me but wanted to check before I shelled out the expense?

Thanks in advance