Changing the form of a whole-bar rest

[David Sumbler]

%%%%%
\version "2.19.48"

\language "english"

{ \time 4/2 R1*4/2 }
%%%%%

The above prints a breve rest in the middle of the bar.

I want the "normal" whole-bar rest to appear instead, i.e. a semibreve
rest.

After much experimentation and searching online and in the Lilypond
docs, the best I have come up with is

%%%%%
\version "2.19.48"

\language "english"

{ \time 4/2
  \once \override MultiMeasureRest.stencil = #ly:text-interface::print
  \once \override MultiMeasureRest.text = \markup \musicglyph "rests.0" 
  R1*4/2 }
%%%%%

This doesn't work correctly, for reasons I can partly understand.  The
required rest does appear, but it is at the beginning of the stave
rather than in the middle of the bar.

How can I get the result I want?

David