  Planetesimals -- asteroids and comets -- are the building blocks of planets
in protoplanetary discs and the source of dust, ice and gas in debris discs.
Along with planets they comprise the left-over material after star formation
that constitutes a planetary system. Planets influence the dynamics of
planetesimals, sculpting the orbits of debris belts to produce asymmetries or
gaps. We can constrain the architecture of planetary systems, and infer the
presence of unseen planetary companions, by high spatial resolution imaging of
debris discs. HD~16743 is a relatively young F-type star that hosts a bright
edge-on debris disc. Based on far-infrared \textit{Herschel} observations its
disc was thought to be stirred by a planetary companion. Here we present the
first spatially resolved observations at near-infrared and millimetre
wavelengths with \textit{HST} and ALMA, revealing the disc to be highly
inclined at $87\fdg3~^{+1\fdg9}_{-2\fdg5}$ with a radial extent of
157.7$^{+2.6}_{-1.5}$~au and a FWHM of 79.4$^{+8.1}_{-7.8}$~au ($\Delta R/R =
0.5$). The vertical scale height of the disc is $0.13~\pm~0.02$, significantly
greater than typically assumed unstirred value of 0.05, and could be indicative
of stirring of the dust-producing planetesimals within the disc by bodies at
least a few times the mass of Pluto up to 18.3~$M_{\oplus}$ in the single
object limit.
