L-H transition experiments have recently been performed on JET to characterise the local edge ion parameters. Evidence of a threshold in the edge ion temperature to access the H-mode is presented and comparisons are made with edge electron temperature. These results provide the first scaling of pedestal ion temperature on JET. The threshold edge ion temperature scales approximately linearly with toroidal magnetic field and shows no dependence on electron density in the range explored. Reference shots have been repeated with "reversed field", with the ion B drift away from the X-point and counter neutral beam injection. In contrast to expectations, the reversed field transitions to H-mode occur at very similar values of input power and at lower edge ion and electron temperatures for a range of densities and toroidal fields. All the L-H transition data is also considered in terms of local edge dimensionless ion parameter space. The effective edge ion collisionality does not appear to play a significant role in the L-H transition, providing no clear distinction between the L and H-modes phases. In contrast, the normalised poloidal ion gyroradius provides a sharp H-mode boundary and could be interpreted as an ion temperature related critical parameter for H-mode access.