The static seal (30) includes a rotary seal body (32) comprising an annular base portion (34) which is drivingly mountable on a rotary component such as a shaft and an annular cantilever portion (40) connected at one end to the base portion (34). The seal (30) 5 further includes a rotary seal face (48) and circumferential weights (44) connected to the cantilever portion (40). The seal is configured to dilate under centrifugal force to provide a running clearance between the rotary seal face and a complementary static seal face with which the rotary seal face is in contact when the rotary seal body (28) is stationary. The rotary seal body is further configured so as to facilitate the breaking up of slurry which may set around the seal when the pump (10) of which the seal forms part is inoperative.