Originally Posted by pem

I think you will find that a Transparent Proxy is one that is invisible to the client, not the server. In other words the client does not know the proxy is there - it thinks it is talking direct to the server. The server will (as posted above) generally think the request is coming from the proxy, not the client.
That is why most "what is my IP" links give the NTL proxy IP and not the client IP. (e.g. http://www.whatismyip.com/ )