A spool valve 10 for a variable camshaft timing (VCT) phaser for an internal combustion engine comprises a spool 11 slidable in a bore 12 in a valve sleeve 13, the spool 11 having spaced apart lands 14-17 dividing the bore 12 into chambers 41, 42, 43 between adjacent lands. The valve sleeve 13 has fluid passages 22-27 including a lock passage 26 communicating with a lock pin 31, a vent passage 27 communicating with a fluid sump 35, and a lock pin oil feed passage 22, with the spool 11 being slidable in the bore 12 to interconnect select passages via particular chambers, wherein the vent passage 27 and the lock pin passage 26 are connectable with different chambers 43 and 42 respectively. The arrangement avoids unnecessary operation of the lock pin 31.