We use focused ion beam (FIB) etching to create suspended photonic crystal cavities in diamond. Our goal is to enhance and control the spontaneous emission of single N-V colour centres, which act like single 'two-level atoms' emitting single photons. The single nitrogen-vacancy (N-V) colour centre in diamond has attracted a lot of interest because it can be optically addressed, is photostable at room temperature and has a paramagnetic ground state whose spin can be initialized and read-out optically. By enclosing the (N-V) colour centre in a resonant cavity we aim to develop rapid readout of this optically addressable single spin. We show a technique using FIB and confocal microscopy to locate single N-V centres and discuss progress towards etching cavities around single centres.