I searched for ages to find the line of code I needed... I ploughed through all the sites offering convoluted solutions, the sites offering JavaScript solutions when the description of the site said ASP ! and I even found sites that wanted to charge me $49 for a script to do this !
All I needed was:
<%@language="VBScript"%>
<%
Response.Write Request.ServerVariables("REMOTE_ADDR")
%>