A rotary piston internal combustion engine includes an engine housing, an output shaft configured to rotate relative to the engine housing about an axis for transmitting power to parts to be operated, a rotary piston mounted eccentrically on the output shaft, a first bearing configured to support and facilitate rotation of the output shaft, the first bearing being sandwiched between a first pair of seals and a second bearing configured to support and facilitate rotation of the rotary piston, the second bearing being sandwiched between a second pair of seals, wherein the output shaft defines an internal path which has a first section to allow a lubricating substance to flow between the first bearing and the second bearing, in use.