When you read the advertisement for the post, you will notice the invitation to meet specified members of the section. It is a sensible idea to at least make some enquiries - even if you don’t intend to actually visit. For one thing it will ensure that your name is on somebody’s radar.
You will obviously need to make an appointment and not just turn up and say “I’m Here!” If the post is a competitive one then it could be possible for 50-100 applicants to all turn up and say “I’m Here!” which would cause chaos for the unit. Some departments will routinely decide to not allow doctors to visit, unless they have been shortlisted.
So the intended outcome for the pre medical interview short-listing visit is for you to discover if it is even worth you applying to the department for a job. However, do not be fooled into believing that the visit won’t be used to valuate you as well. Be well organised so that you can use the visit to sell your skills to the unit and make a decent first impression.
Some sections have unuttered rules that they will not consider a consultant physician interview application for short listing unless they have made a pre shortlisting visit.