Isolated Leptons and Missing P_{T} at HERA

The search for events containing isolated leptons (electrons or muons) and missing transverse momentum produced in e^{\pm}p collisions is performed individually and in a common phase space with the H1 and ZEUS detectors at HERA in the period 1994--2007. The analysed H1+ZEUS data sample corresponds to an integrated luminosity of 0.97 fb^{-1}, and composes of the complete high energy data from the HERA programme. A total of 87 events are observed in the data, compared to a Standard Model (SM) prediction of 92.7 \pm 11.2. At large hadronic transverse momentum P_{T}^{X} > 25 GeV in the e^{+}p data, luminosity 0.58 fb^{-1}, 23 data events are observed compared to a SM prediction of 14.6 \pm 1.9. Production cross section measurements of events containing isolated leptons and missing transverse momentum and single W production, as well as W polarisation fractions performed by the H1 Collaboration are also presented. The H1 isolated lepton events are also examined in the context of a search for single top production.