A continuous process for the tetramerisation of ethylene, the process including: a) providing an activated catalyst comprising: i) a source of chromium; ii) a ligating compound of the formula R 1 R 2 P 1 XP 2 R 3 R 4 wherein P 1 and P 2 are phosphorus atoms; X is a linking group between P 1 and P 2, such that any heteroatom on the shortest connecting path between P 1 and P 2 is either bound to P 1 or P 2 or adjacent to an atom bound to P 1 or P 2; and R 1 to R 4 are independently a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group; and iii) optionally a catalyst activator or combination of catalyst activators; and b) contacting ethylene to be tetramerised with the activated catalyst at a reaction temperature of from above 80°C to 115°C, thereby to form at least 30% 1-octene and a polyethylene co-product that, together with any other reaction products, remain substantially dissolved in the liquid phase, the polyethylene co-product being characterised as having: i) a weight average molecular weight (Mw), as determined by gel permeation chromatography, of less than 200 000 g/mol; ii) a number average molecular weight (Mn), as determined by gel permeation chromatography, of less than 3 000 g/mol; and iii) a melt flow index, as determined by ASTM method D1238 at 190°C and 21.6kg, of more than 20 g/10 minutes. a) providing an activated catalyst comprising: i) a source of chromium; ii) a ligating compound of the formula R 1 R 2 P 1 XP 2 R 3 R 4 wherein P 1 and P 2 are phosphorus atoms; X is a linking group between P 1 and P 2, such that any heteroatom on the shortest connecting path between P 1 and P 2 is either bound to P 1 or P 2 or adjacent to an atom bound to P 1 or P 2; and R 1 to R 4 are independently a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group; and iii) optionally a catalyst activator or combination of catalyst activators; and i) a source of chromium; ii) a ligating compound of the formula R 1 R 2 P 1 XP 2 R 3 R 4 wherein P 1 and P 2 are phosphorus atoms; X is a linking group between P 1 and P 2, such that any heteroatom on the shortest connecting path between P 1 and P 2 is either bound to P 1 or P 2 or adjacent to an atom bound to P 1 or P 2; and R 1 to R 4 are independently a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group; and wherein P 1 and P 2 are phosphorus atoms; X is a linking group between P 1 and P 2, such that any heteroatom on the shortest connecting path between P 1 and P 2 is either bound to P 1 or P 2 or adjacent to an atom bound to P 1 or P 2; and R 1 to R 4 are independently a hydrocarbyl group, an organoheteryl group or a heterohydrocarbyl group; and iii) optionally a catalyst activator or combination of catalyst activators; and b) contacting ethylene to be tetramerised with the activated catalyst at a reaction temperature of from above 80°C to 115°C, thereby to form at least 30% 1-octene and a polyethylene co-product that, together with any other reaction products, remain substantially dissolved in the liquid phase, the polyethylene co-product being characterised as having: i) a weight average molecular weight (Mw), as determined by gel permeation chromatography, of less than 200 000 g/mol; ii) a number average molecular weight (Mn), as determined by gel permeation chromatography, of less than 3 000 g/mol; and iii) a melt flow index, as determined by ASTM method D1238 at 190°C and 21.6kg, of more than 20 g/10 minutes. i) a weight average molecular weight (Mw), as determined by gel permeation chromatography, of less than 200 000 g/mol; ii) a number average molecular weight (Mn), as determined by gel permeation chromatography, of less than 3 000 g/mol; and iii) a melt flow index, as determined by ASTM method D1238 at 190°C and 21.6kg, of more than 20 g/10 minutes.