Sandi Toksvig looks at the simplicity and versatility of the bicycle as a travel machine with three very different cyclists. Susie Wheeldon rode 22,000 kilometres around the world, crossing deserts from Tunisia to Arizona, as she and her companions were researching solar energy. Robert Penn leads cycling weekends in the hills of the Brecon Beacons where the ups are as satisfying as the downs. And Matt Carroll recommends day trips in some of England's most beautiful countryside. Together they discuss the feeling of freedom realised in today's world by a device which hasn't changed its basic design for over 130 years. Producer: Harry Parker.