[en] A search for single top quark production is performed in the full e^±p data sample collected by the H1 experiment at HERA, corresponding to an integrated luminosity of 474 pb^-1. Decays of top quarks into a b quark and a W boson with subsequent leptonic or hadronic decay of the W are investigated. A multivariate analysis is performed to discriminate top quark production from Standard Model background processes. An upper limit on the top quark production cross section via flavour changing neutral current processes σ(ep→etX)<0.25 pb is established at 95% CL. Limits on the anomalous coupling κ_tuγ are derived.