title: The Newtonian constant of gravitation-a constant too difficult to measure? An introduction.
authors.affiliation: BIPM, Pavillon de Breteuil, 92312 Sèvres Cedex, France tjqfrs@gmail.com.
authors.forename: Terry
authors.initials: T
authors.lastname: Quinn
authors.affiliation: School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Clive
authors.initials: C
authors.lastname: Speake
keywords: experimental gravitational physics; gravity; metrology