Context : Hyper-velocity stars are suggested to originate from the dynamical interaction of binary stars with the supermassive black hole in the Galactic centre ( GC ) , which accelerates one component of the binary to beyond the Galactic escape velocity . Aims : The evolutionary status and GC origin of the hyper-velocity star SDSS J113312.12+010824.9 ( aka HVS 7 ) is constrained from a detailed study of its stellar parameters and chemical composition . Methods : High-resolution spectra of HVS 7 obtained with UVES on the ESO VLT were analysed using state-of-the-art NLTE/LTE modelling techniques that can account for a chemically-peculiar composition via opacity sampling . Results : Instead of the expected slight enrichments of \alpha -elements and near-solar iron , huge chemical peculiarities of all elements are apparent . The helium abundance is very low ( < 1/100 solar ) , C , N and O are below the detection limit , i.e they are underabundant ( < 1/100 , \lesssim 1/3 and < 1/10 solar ) . Heavier elements , however , are overabundant : the iron group by a factor of \sim 10 , P , Co and Cl by factors \sim 40 , 80 and 440 and rare-earth elements and mercury even by \sim 10 000 . An additional finding , relevant also for other chemically peculiar stars are the large NLTE effects on abundances of Ti ii and Fe ii ( \sim 0.6–0.7 dex ) . The derived abundance pattern of HVS 7 is characteristic for the class of chemical peculiar magnetic B stars on the main sequence . The chemical composition and high projected rotation velocity v \sin i = 55 \pm 2 km s ^ { -1 } render a low mass nature of HVS 7 as a blue horizontal branch star unlikely . Conclusions : Such a surface abundance pattern is caused by atomic diffusion in a possibly magnetically stabilised , non-convective atmosphere . Hence all chemical information on the star ’ s place of birth and its evolution has been washed out . High precision astrometry is the only means to validate a GC origin for HVS 7 .