DOWNHOLE TOOL
A downhole tool (10) comprises a body (12) adapted to be incorporated in a drill string. The body defines a bore (20) and having a valve arrangement including a flow port (18) in the wall of the body and a valve element (22) biased towards a position to open the port. The valve element is initially retained in a position to close the flow port (18) but can be released as required to allow the flow port to be opened. The tool may be utilized as a bypass sub or a dump sub. For use as a bypass sub, the body bore below the flow port may be closed or restricted.