A torque sensor (107; 207; 307; 407; 507) for use in an electric power assisted steering system comprising: a first shaft, a second shaft (102b; 202b; 302b; 402b; 502b), and a torsion bar (116; 216; 316; 416; 516) that connects the first shaft to the second shaft (102b; 202b; 302b; 402b; 502b), a hollow sleeve (112; 212; 312; 412; 512) that is secured at a first position to the first shaft and extends along the torsion bar (116; 216; 316; 416; 516) to at least partially axially overlap the second shaft (102b; 202b; 302b; 402b; 502b), angular deflection indicating means that produce a signal that is dependent on the angular deflection of the first shaft relative to the second shaft (102b; 202b; 302b; 402b; 502b) as a torque is applied across the torque sensor (107; 207; 307; 407; 507) that causes the torsion bar (116; 216; 316; 416; 516) to twist, at least one drive dog fixed to the sleeve (112; 212; 312; 412; 512) and at least one corresponding drive dog (118b; 218b; 318b; 418b; 518b) fixed to the second shaft (102b; 202b; 302b; 402b; 502b), in normal operation the two dogs (118a, 118b; 218b; 318b; 418b; 518b) being offset so that they permit a defined range of angular deflection of the torsion bar (116; 216; 316; 416; 516) but will engage each other to provide a path for torque to be transferred from the first shaft to the second shaft (102b; 202b; 302b; 402b; 502b) in the event of a failure of the torsion bar (116; 216; 316; 416; 516), and characterised by further comprising a connecting element (119; 219; 319; 419; 519) which has a first part that is secured within a bore (220; 320; 420; 520) in one of the second shaft (102b; 202b; 302b; 402b; 502b) and the sleeve (112; 212; 312; 412; 512), the connecting element (119; 219; 319; 419; 519) having a second part that extends into a feature of the other of the second shaft (102b; 202b; 302b; 402b; 502b) and the sleeve (112; 212; 312; 412; 512), at zero torque across the torque sensor (107; 207; 307; 407; 507) the connecting element (119; 219; 319; 419; 519) being spaced from the feature in a direction along the axis of the shafts that is less than the overlap of the drive dogs (118a, 118b; 218b; 318b; 418b; 518b) in that direction to prevent the shafts (102a, 102b; 202b; 302b; 402b; 502b) moving apart in the event of failure of the torsion bar (116; 216; 316; 416; 516) by an amount that would otherwise prevent the drive dogs (118a, 118b; 218b; 318b; 418b; 518b) engaging, and wherein the connecting element (119; 219; 319; 419; 519) and said feature are arranged such that the connecting element (119; 219; 319; 419; 519) does not contact said feature as a result of rotation of the first part relative to the second part. a first shaft, a second shaft (102b; 202b; 302b; 402b; 502b), and a torsion bar (116; 216; 316; 416; 516) that connects the first shaft to the second shaft (102b; 202b; 302b; 402b; 502b), a hollow sleeve (112; 212; 312; 412; 512) that is secured at a first position to the first shaft and extends along the torsion bar (116; 216; 316; 416; 516) to at least partially axially overlap the second shaft (102b; 202b; 302b; 402b; 502b), angular deflection indicating means that produce a signal that is dependent on the angular deflection of the first shaft relative to the second shaft (102b; 202b; 302b; 402b; 502b) as a torque is applied across the torque sensor (107; 207; 307; 407; 507) that causes the torsion bar (116; 216; 316; 416; 516) to twist, at least one drive dog fixed to the sleeve (112; 212; 312; 412; 512) and at least one corresponding drive dog (118b; 218b; 318b; 418b; 518b) fixed to the second shaft (102b; 202b; 302b; 402b; 502b), in normal operation the two dogs (118a, 118b; 218b; 318b; 418b; 518b) being offset so that they permit a defined range of angular deflection of the torsion bar (116; 216; 316; 416; 516) but will engage each other to provide a path for torque to be transferred from the first shaft to the second shaft (102b; 202b; 302b; 402b; 502b) in the event of a failure of the torsion bar (116; 216; 316; 416; 516), and characterised by further comprising a connecting element (119; 219; 319; 419; 519) which has a first part that is secured within a bore (220; 320; 420; 520) in one of the second shaft (102b; 202b; 302b; 402b; 502b) and the sleeve (112; 212; 312; 412; 512), the connecting element (119; 219; 319; 419; 519) having a second part that extends into a feature of the other of the second shaft (102b; 202b; 302b; 402b; 502b) and the sleeve (112; 212; 312; 412; 512), at zero torque across the torque sensor (107; 207; 307; 407; 507) the connecting element (119; 219; 319; 419; 519) being spaced from the feature in a direction along the axis of the shafts that is less than the overlap of the drive dogs (118a, 118b; 218b; 318b; 418b; 518b) in that direction to prevent the shafts (102a, 102b; 202b; 302b; 402b; 502b) moving apart in the event of failure of the torsion bar (116; 216; 316; 416; 516) by an amount that would otherwise prevent the drive dogs (118a, 118b; 218b; 318b; 418b; 518b) engaging, and wherein the connecting element (119; 219; 319; 419; 519) and said feature are arranged such that the connecting element (119; 219; 319; 419; 519) does not contact said feature as a result of rotation of the first part relative to the second part.