safari does not give access to Natwest online banking

If using Safari 11, Safari/Preferences/Privacy to make sure Block all cookies isn't checked. If that doesn't work, in the same pane, uncheck Prevent cross-site tracking.

Looking at the Natwest Online Banking website, I see that your browser has to be set to accept cookies in order for you to gain access to their site.

On Safari, choose the Safari menu, then Preferences, and finally Security. Choose to accept cookies - either always, or 'from sites I visit'.

You should now be able to access the Natwest site with Safari.