Hi Albo - let's take it up a level and start with the presumption that the site manager would have SMSTS. Very few would be of the view that this manager does nothing other than oversee site health and safety. They will reviewing progress against programme, liaising with client, designers etc and all the subbies amongst other tasks.

So, why would it be necessary for a supervisor (with SSSTS) do nothing other than oversee site health and safety?

Noting that there is nothing in law that dictates SMSTS and SSSTS as being prescribed, but that these or accepted equivalents are the generally expected standards in the better end of the construction industry the level of management and supervision that is directly related to health and safety will need to vary according to the size and compexity of the construction site.

So, on a small utility scheme with may be five workers it seems to me that it would be fine for the supervisor to also do something else. In contrast if building a supermarket you would probably need several supervisors though perhaps none doing nothing but overseeing site health and safety.

May be that utility scheme involves working on the road and the need for a traffic management supervisor. Might be the SSSTS supervisor, might be someone else.

Conversely, if you are building a supermarket, you probably need multiple supervisors, but even then it is likely to be rare that they have no duties other than H&S.

All dependent on the ubiquitous "risk assessment" + whatever rules the client. Principal Contractor or individual contractors apply.

In ye olden days the Construction (General Provisions) Regulations 1961 said that any site with 20 or more workers needed to have a "safety supervisor" - but rarely was that requirement complied with by having someone dedicated full time to safety issues. Usually it was the site manager or foreman (no forewomen in those days) with some training - exactly how the SMSTS and SSSTS schemes came into being. The role was often topped up by getting intermittent visits by a health and safety bod, whether employed by the contractor or a consultant turning up typically once a month.