The last 80 years have seen significant changes in industrial technologies, with the development of composite materials being particularly striking. These were hardly present before the Second World War but were made possible by the availability of new polymers, fibre reinforcements and innovative manufacturing techniques. In parallel, the traditional flax farming practices for the textile industry have benefited from major improvements in seed selection, retting and fibre extraction methods. This aims of this paper are twofold; first to describe the early work to develop flax fibre reinforced composites and compare their mechanical properties with those of contemporary flax fibres. And second, to understand the impact of significant efforts made recently to improve flax fibre production. The simple substitution of synthetic fibres is no longer sufficient to justify their use; their environmental benefits must be demonstrated, through life cycle analyses to support sustainable societal choices, and these are also discussed.