The development of multi-Petawatt lasers and particle beams allows the investigation of extreme field physics. With laser intensities of the order 10^23 W/cm^2, it is now possible to investigate the nonlinear vacuum or strong field QED. The Central Laser Facility is currently building two new laser systems to investigate the intensity frontier, namely the Extreme Photonics Applications Centre (EPAC) and Vulcan 20-20. These lasers will be capable of generating multi-GeV electron beams and are possible routes to TeV particle beams. I will review some of the topics that will be investigated by these new laser systems, such as photon-photon scattering, electron-positron pair plasmas, and the possible detection of Unruh radiation. I will also discuss possible future directions involving photon-axion coupling, considering the possibility of parametrically coupling intense laser beams to axions via three and four-wave nonlinear scattering. Photon-axion coupling has similarities to photon-gravitational wave coupling, known as the Gertsenshtein effect and the interaction of Intense neutrino beams with longitudinal photons.