Why does Writer show two pages side by side?

I am using the latest U.S. LO Writer with the current Linux Mint on a PC, with a Lenovo monitor in portrait mode. For some reason, yesterday Writer started showing all files that I open with two pages (not two columns) across. This is a royal pain to use in portrait mode. I have never voluntarily opened a file in two-across mode. I can’t find anything in the menus to correct this glitch. How can I fix it?

Question is duplicate of those here and here.

Question 32504 may well be a duplicate question. However, a google search for “libreoffice single double page view layout” lead me to this page as the first choice. That said, 4091 does provide me with the correct answer to reset the layout to a one-page view as I do not have the items mentioned below in the status bar, and although I’ve now added ‘zoom’ to the standard toolbar it does not resemble as below.

It is likely a wrong setting in the status bar, near the zoom glider. There you find “one page”, “multiple pages”, “book view”.image description

See also libreoffice-writer new document begins on right side of screen