[Tex/LaTex] Can’t break a line in \maketitle with \raggedright

horizontal alignmenttitles

(This is, in a sense, a follow-up to Insert text between title and author).

When using \raggedright in the preamble, LaTeX throws an error when I use a linebreak command \\ in \maketitle. How can I circumvent this?

\documentclass{article}
\raggedright % turn off right-edge text justification and hyphenation
\usepackage{titling}
    \pretitle{\begin{flushleft}\LARGE\textbf} % left aligned title with LARGE bold type
    \posttitle{\vskip .25ex\hrule\par\end{flushleft}} % add hrule under title
    \preauthor{\begin{flushleft}\large} % left align author
    \postauthor{\par\end{flushleft}}
    \predate{\begin{flushleft}} % left align date
    \postdate{\par\end{flushleft}\vspace{-3ex}} % reduce space after \maketitle

\begin{document}
\title{Review}
\author{\textbf{Paul McCartney}\\ University of Liverpool}
\date{\today}
\maketitle
\noindent Here my review begins
\end{document}

! Argument of \reserved@a has an extra }.

\par

l.14 …Paul McCartney}\ University of Liverpool}

Best Answer

Usually (not always, but here) 

! Argument of \reserved@a has an extra }.

should be read as Use of fragile command in a moving argument.

So

\author{\textbf{Paul McCartney}\protect\\ University of Liverpool}

Works as intended without error.

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