Abstract: A process for the production of liquid meta-rich triaryl phosphate esters having low triphenyl phosphate content and low viscosity comprises (a) an alkylation stage wherein a phenol is reacted with an olefin having 2 to 12 carbon atoms in the presence of a strong acid catalyst to give a reaction product comprising a mixture of meta and para alkylated phenols; and (b) a transalkylation stage wherein the mixture of alkylated phenols from the alkylation stage is heated in the presence of a strong acid catalyst to increase the meta isomer content of the mixture to at least 25% whilst maintaining a phenol level below 22%; and (c) a phosphorylation stage wherein the mixture of alkylated phenols from the transalkylation stage is reacted with a phosphorylating agent; and wherein the strong acid catalyst used in stages (a) and (b) is a Bronsted acid having an acid strength of less than zero. Preferred catalysts are activated clays such as bentonite, montmorillonite or Fullers Earth clay.