Abstract: A method of forming a cast-in-situ pile with an enlarged head, wherein a collar (1,13) is releasably affixed to the lower end of a piling tool (10) and the piling tool (10) and the collar (1,13) are driven to a first depth and the collar (1,13) is released from the piling tool (10). The piling tool (10) is then driven to a second depth, the piling tool (10) passing freely through a central aperture (2,14) of the collar (1,13), which remains at the first depth. The piling tool (10) is then withdrawn, and concrete or grout (20) is supplied to the lower end of the piling tool so as to form a cast-in-situ pile (22). When the lower end of the piling tool (10) again reaches the first depth, the collar (1,13) is lifted from the ground and concrete or grout (20) is supplied into the void left thereby so as to form a pile (22) with an enlarged head (23).