Sherrington and co-workers have shown that branched vinyl polymers can be synthesized by the addition of a chain transfer agent to a conventional free radical statistical copolymerisation of a vinyl and a divinyl monomer. In the presence of the chain transfer agent, the molecular weight of the primary chains is reduced, gelation can be suppressed and soluble, branched polymers are obtained as the sole product. Living polymerisation techniques offer a way to control the primary chain length without the need for a transfer agent simply by adjusting the monomer/initiator molar ratio. It is suggested that a significant degree of intramolecular cyclisation is the most likely explanation for the remarkable delay in the onset of gelation.