  The presence of dark matter is nowadays widely supported by a large body of
astronomical and cosmological observations. A large amount of dark matter is
expected to be present in the central region of the Milky Way. Very-high-energy
(>100 GeV) {\gamma}-rays can be produced in the annihilation of dark matter
particles. The H.E.S.S. array of Imaging Atmospheric Cherenkov Telescopes is a
powerful tools to observe the Galactic Centre trying to detect {\gamma}-rays
from dark matter annihilation. A new search for a dark matter signal has been
carried out on the full H.E.S.S.-I data set of 2004-2014 observations. A
2D-binned likelihood method has been applied to exploit the spectral and
spatial properties of signal and background. Updated constraints are derived on
the velocity-weighted annihilation cross section for signals from prompt
annihilation of dark matter particles into two photons. The larger statistics
from the 10-year Galactic Center dataset of H.E.S.S.-I together with the
2D-analysis technique allows to significantly improve the previous limits.
