Method for starting and operating an internal combustion engine

A method is provided for operating an internal combustion engine comprising a combustion chamber defined by the inner wall of a cylinder, a cylinder head 18 and the upper surface of a piston 12 moveable longitudinally within the cylinder, the engine further comprising a pre-combustion chamber 26 in communication with the combustion chamber. The method comprises supplying to the combustion chamber a first combustible mixture of a first hydrocarbon fuel and oxygen; supplying to the pre-combustion chamber 26 a second combustible mixture of a second hydrocarbon fuel and oxygen, the second combustible mixture being auto-ignitable; and compressing the first and second combustible mixtures by moving the piston within the cylinder; wherein under operating conditions in which the aforementioned steps are insufficient to operate the engine and keep it running, the method further comprises the step of generating a spark to cause ignition of the compressed first combustible mixture in the combustion chamber. An internal combustion engine 2 operable using this method is also provided. In addition, a cylinder head 18 for the modification of existing engines to operate using this method is also provided. The method is particularly useful for starting the internal combustion engine, especially when cold.