Recent developments in coronagraphy have increased the reachable dynamic range limit of telescopes and thus opened the possibility for the imaging of fainter and fainter companions. They rely on a series of modifications of the original concept involving amplitude and phase masks in either the pupil or the image plane. They are designed to operate optimally at one wavelength. In this paper we first study the chromatic leakage in Pupil Apodised Lyot Coronagraphs and then present a theoretical solution that create a polychromatic null while maximizing the photon flux from the companion. Finally we discuss a promising experimental implementation of this solution using interferometric apodisations.