The invention provides a method of alkene metathesis comprising contacting at least a first alkene, which is cardanol and/or anacardic acid, with an alkylidene ruthenium alkene metathesis catalyst comprising two ligands P1 and P2, which may be the same or different and of formula P(R1)3, in which P is a phosphorus atom coordinated to the ruthenium ion and each R1 is independently an optionally substituted alkyl or alkoxy group; or two R1 groups within one P1 or P2 ligand constitute an optionally substituted bicycloalkyl.