ICRF mode conversion has been shown to drive toroidal flow in JET D(3He) L-mode plasmas: Bt0 = 3.45T, ne0 ~ 3 x 1019 m-3, Ip = 2.8 and 1.8MA, PRF 3MW @ 33MHz and -90o phase. Central toroidal rotation in the counter-Ip direction, with 0 up to 10 krad/s (Vϕ0 ~ 30km/s, central thermal Mach number Mth(0) ~ 0.07, and Alfven Mach number MA(0) ~ 0.003) has been observed. The flow drive effect is sensitive to the 3He concentration and the largest rotation is observed in the range of nHe3/ne ~ 10%-17%. The rotation profile is peaked near the magnetic axis, and the central rotation scales with the input RF power. The effective torque density profile from the RF power has been calculated and the total torque is estimated to be as high as 50% of the same power from neutral beam injection, and a factor of 5 larger than the direct momentum injection from the RF waves. RF physics modeling using the TORIC code shows that the interaction between the mode converted ion cyclotron wave and the 3He ions, and associated asymmetry in space and momentum may be key for flow drive.