Relationship created by Look Up wizard

I have created a Client table, a Contract table and an Invoice table.

In the Contract table, I have used the Look up wizard to create a relationship with the Client table to give me a list of current Client names from the Client table.

This appears to work OK until I look into the relationship, at which point I see that the wizard has created the relationship between Client ID in the Client table and not with Client Name in the Client table.

Although this doesn't effect this particular look up/relationship, it seems to be having a knock on effect further down the line when I try and create a look up in the Invoice table back to the Client table to again look for a Client Name. Instead of giving me the name, it is giving me the Client ID.

Why is it not linking Client Name in the Client table with Client Name in hte Contract table? Is this something to do with the Client ID being the primary key?