A cutting tool adapted to be deployed into a well casing for cutting through casing strings comprises a nozzle for directing a jet of an abrasive slurry at the wall of a well casing to sever the well casing and a mechanical locking arranged provided above the nozzle, said locking arrangement comprises radially expandable means selectively engageable with an inner wall of the well casing within which the tool is deployed, to prevent axial and/or rotational movement of the tool in the well during cutting operations.