A process (200) to synthesise hydrocarbons includes gasifying (12) a carbonaceous feed material at a temperature sufficiently high to produce at least one hot synthesis gas stream (42) at a temperature of at least 900° C. and comprising at least CO and H2. In a Fischer-Tropsch hydrocarbon synthesis stage (22), synthesis gas is converted to hydrocarbons, providing a tail gas stream (40) containing methane. The tail gas stream (40) is subjected to steam reforming (30) thereby converting the methane to CO and H2 producing a reformed gas stream which is recycled to the Fischer-Tropsch hydrocarbon synthesis stage (22). The steam reforming (30) takes place at an elevated temperature of at least 700° C. and heat for the steam reforming is provided by indirect heat exchange with the at least one hot synthesis gas stream (42).