Dykes was educated at Weston-super-Mare Grammar School, Somerset, followed by Pembroke College, Cambridge.

He married Susan Margaret Smith in 1966 and they had three sons; Oliver, Jonathan and Jethro.

While an MP, Dykes served in the Ministry of Defence and the Cabinet Office in Edward Heath's government.

Following the defeat of Kenneth Clarke in the Conservative leadership contest following the 1997 general election, Dykes joined the Liberal Democrats.

Within a year of joining the party, he came to serve as an adviser to Paddy Ashdown on European Union affairs.