The present invention relates to an internal combustion engine comprising: a plurality of combustion chambers (41,42,43,44); an air induction system (45,45A,45B,46,47) for delivering air to each combustion chamber (41,42,43,44); a fuel system for delivering fuel to each combustion chamber (41,42,43,44); an exhaust system (48,50) for relaying combusted gases from the combustion chambers (41,42,43,44) to atmosphere; and an exhaust recirculation system (49,51) to relay combusted gases from the exhaust system (48,50) to at least one of the combustion chambers (42,43). The engine has a chamber deactivation operating mode in which at least one combustion chamber (41,44) is active and receives fuel and air which are combusted therein and at least one other combustion chamber (42,43) is deactivated and is supplied with no fuel by the fuel system. In the chamber deactivation operating mode the exhaust gas recirculation system (49,51) supplies combusted gas to the (or each) deactivated combustion chamber (42,43).