You want to know if the login page is NatWest?
Click on the Login link and look at the browsers security bar.
If it says "The Royal Bank of Scotland Group Plc [GB]" and that then entity with which you do business, great.
It seems as if Troy would be just fine with HTTPS rather than HTTP, but DV validated certs aren't what you want anyway with a financial institution.
It seems far more likely that you care about the entity you are working with (Royal Bank of Scotland), than the domain of the referring page (personal.natwest.com).