After the successful completion of the 2010-2011 shut down, JET resumed operation with completely new Plasma Facing Components (PFCs) consisting of a tungsten (W) divertor and a beryllium (Be) inner wall complemented by some W tiles in small crucial areas [1]. These materials, as well as the shape of the plasmas they interact with, mimic very closely the scenarios foreseen for ITER especially when JET is run at high triangularity (d~0.35). Operation was resumed with ohmic or slightly additionally heated L-mode discharges, in order to safely explore the effect of the new wall on fuelling efficiency, density limit, recycling, detachment, impurity behaviour and confinement. One of the main reasons for turning to metals as PFCs, in spite of the remarkable capability of carbon to withstand large power fluxes and to yield intrinsic edge radiation, was to reduce the fuel retention, which in ITER would quickly saturate the maximum allowed tritium inventory. L-mode operation with the new wall at JET has immediately shown the beneficial effect of the new materials to this regard [2].