Found by right clicking on a tool bar and selecting 'Customise / Appearance...', then navigate to 'Buttons (tab) / Browser view' and dragging the '> Go' button onto the tool bar containing the address bar and clicking the 'Appearance' windows 'Ok' button to confirm the the changes.
That trick does not work with the Windows version of Opera. I think the Linux version still uses the old engine as opposed to webkit. I think...