  The top quark mass has been measured using the template method in the top
antitop -> lepton + jets channel based on data recorded in 2011 with the ATLAS
detector at the LHC. The data were taken at a proton-proton centre-of-mass
energy of sqrt(s) = 7 TeV and correspond to an integrated luminosity of
1.04/fb. The analyses in the electron + jets and muon + jets decay channels
yield consistent results. The top quark mass is measured to be m_top = 174.5
+/- 0.6_stat +/- 2.3_syst GeV.
