A power transmitter for wireless power transfer to a power receiver using an electromagnetic power transfer signal, the power transmitter comprising: a power transfer coil for generating the power transfer signal; a controller for controlling the power transmitter to perform power transfer during a power transfer phase, the power transfer phase comprising power transfer intervals where power is transferred and foreign object detection time intervals during which a power level of the power transfer signal is reduced; a foreign object detection antenna; and a foreign object detector arranged to generate a drive signal to drive the foreign object detection antenna to generate a foreign object detection electromagnetic test signal during foreign object detection time intervals and perform foreign object detection in response to the drive signal; and the power transmitter being characterised by comprising: a magnetic shielding element (503, 505) positioned between the power transfer coil (103, 107) and a power transfer coil of the power receiver during power transfer operation; and where the magnetic shielding element (503, 505) is positioned between the power transfer coil and the foreign object detection antenna; wherein the magnetic shielding element (503, 505) comprises a magnetic shield material having a saturation point such that it operates in a saturated mode during power transfer intervals and in a non-saturated mode during the foreign object detection time intervals, the saturation point being below a magnetic field strength generated by the power transfer signal during the power transfer time intervals and above a magnetic field strength generated during the foreign object detection time intervals. a power transfer coil for generating the power transfer signal; a controller for controlling the power transmitter to perform power transfer during a power transfer phase, the power transfer phase comprising power transfer intervals where power is transferred and foreign object detection time intervals during which a power level of the power transfer signal is reduced; a foreign object detection antenna; and a foreign object detector arranged to generate a drive signal to drive the foreign object detection antenna to generate a foreign object detection electromagnetic test signal during foreign object detection time intervals and perform foreign object detection in response to the drive signal; a magnetic shielding element (503, 505) positioned between the power transfer coil (103, 107) and a power transfer coil of the power receiver during power transfer operation; and where the magnetic shielding element (503, 505) is positioned between the power transfer coil and the foreign object detection antenna; wherein the magnetic shielding element (503, 505) comprises a magnetic shield material having a saturation point such that it operates in a saturated mode during power transfer intervals and in a non-saturated mode during the foreign object detection time intervals, the saturation point being below a magnetic field strength generated by the power transfer signal during the power transfer time intervals and above a magnetic field strength generated during the foreign object detection time intervals.