Rapid tectonic loading of wet sediment in accretionary wedges is likely to cause the fluid pressure to rise until it is sufficient to cause dilatant fracturing. Dewatering of sediment that has been underthrust and accreted beneath the wedge can produce a large steady supply of such highly overpressured fluid. Dilatant fracturing will create escape routes, so the fluid pressure is likely to be buffered at the value required for the transition between shear and oblique tensile (dilatant) fracture, which is slightly in excess of the load pressure if the maximum compression is nearly horizontal. This in turn buffers the strength of the wedge at the cohesive strength, which is not pressure‐dependent, and will not vary greatly throughout the wedge. Near the wedge front the strength is likely to be that of the cohesion on existing thrust faults in the wedge. The shear resistance on the base of the wedge will also be fairly constant and related to the cohesive strength of the weak sediment layer that acts as the basal detachment. These assumptions allow the application of a simple plastic continuum model, which successfully predicts the observed gently convex taper of accretionary wedges. They also allow the use of a mechanical model for frontal imbrication, which predicts the spacing of imbricate thrusts at the front of the wedge from the strength and thickness of the imbricated layer, the ramp angle, and the factional resistances on the bounding faults and décollement surfaces. Reconstruction of thrust geometries from seismic data across the Makran and other accretionary wedges allows the determination of the geometrical parameters, and the thrust imbrication model allows the mechanical parameters to be calculated in terms of an assumed cohesive strength for the incoming sediment layer. The calculated values are reasonable, and successful forward modelling of the profile of the Makran shows that the postulate of a buffered value, of fluid pressure in excess of the load pressure is consistent with observation.