A piston arrangement comprising a piston movable within a cylinder and having a stroke with a first end and a second end, wherein the piston is coupled to a crankshaft by a linkage mechanism including a toggle link which is pivotally coupled to the piston and pivotally coupled to a con-rod, wherein the toggle link has a first position corresponding to the first end of the piston stroke, a second position different to the first position also corresponding to the first end of the piston stroke, and an intermediate position between the first and second positions corresponding to the second end of the piston stroke such that the piston completes four strokes for every one revolution of the crankshaft. Also a piston arrangement comprising first and second pistons movable respectively within first and second cylinders, wherein the first piston is coupled to a crank shaft by a first linkage mechanism including a first toggle link pivotally connected to the first piston and pivotally connected to a first con-rod, wherein the second piston is coupled to the crank shaft by a second linkage mechanism including a second toggle link pivotally connected to the second piston and pivotally connected to a second con-rod, wherein the first and second con-rods have different lengths such that the first and second pistons operate out of phase with each other. Also an engine comprising at least two high pressure pistons movable within respective high pressure cylinders and at least one low pressure piston movable within a low pressure cylinder, wherein the low pressure piston moves through twice the number of strokes moved through by each of the high pressure pistons in the same period of time, wherein a linkage mechanism coupling the low pressure piston to a crankshaft includes a toggle link.