A bit like a business must have a Company Secretary, so a local authority must have a Proper Officer. The role carries with it a number of duties which are enshrined in legislation so without a Proper Officer, the council cannot function. If the council wishes to separate out the functions of the Proper Officer and clerk, so be it but potentially a bit inefficient in terms of cost to have two employees rather than one. Some councils also separate out the RFO function (Responsible Financial Officer) too.