The invention provides a cationic lipid comprising: (i) one head group, comprising one or more amino acids, in which at least one amino acid has a side chain that comprises a cationic moiety or a cationic precursor (ii) a linking moiety of formula (5): &mdash(HNR5)2NC(O)R3C(O)&mdash&emsp&emsp(5), wherein: each R5 is independently an optionally substituted C1-4 alkylene moiety and R3 is an optionally substituted alkylene or alkenylene moiety and (iii) two lipophilic moieties, wherein the head group and each of the lipophilic moieties are connected to the linking moiety through amide linkages.
