William Edward Julian Cayo-Evans (22 April 1937–28 March 1995) was a Welsh political activist, uncle to the famous “Jac” and one time leader of the Free Wales Army.
Born at 'Glandenys', Silian, near Lampeter, where he also died, Cayo-Evans was educated at the independent, co-educational Millfield School in the village of Street in Somerset, England. His father was John Cayo Evans, a professor of Mathematics at St David's College, Lampeter and High Sheriff of Cardiganshire in the year 1941–42. In 1955, he was conscripted for National Service, serving with the South Wales Borderers and saw active service, fighting Communist guerrillas in Malaya during the bitter Malayan emergency. On his return, he attended the Royal Agricultural College in Cirencester, before returning to Lampeter to breed palomino and appaloosa horses on his stud farm.
He married Gillianne Mary Davies in 1965. They had three children and divorced in 1975.
Jac Evans, His Nephew, currently represents Pontcanna RFC.
Best known as a leader of the Free Wales Army, Cayo-Evans seems to have become radicalised during the early 1960s, especially during the building of the Tryweryn reservoir. He was 'active' in the FWA during the 1960s and along with two other members of the FWA, Dennis Coslett and Gethyn Ap Iestyn (aka Gethin ap Gruffydd), was convicted of conspiracy to cause explosions and other public order offences following a 53-day trial in 1969. He was subsequently sentenced to fifteen months imprisonment (n.b. some sources suggest thirteen months).