Born in Bath, Somerset, he lived as a child in Singapore, where his father was stationed in the Royal Air Force, before returning to settle with relatives in Barnsley, Yorkshire.
After attending university, he spent time with the RAF in Europe, and started writing concert reviews of American jazz musicians, which he submitted to such magazines as the New Musical Express and Jazz Journal.
Hawker wrote the lyrics for several songs recorded by Shapiro, including "Don't Treat Me Like a Child", "You Don't Know", and "Walkin' Back to Happiness", for which he won an Ivor Novello award.
In 1973, he co-wrote Cliff Richard's hit single "Help It Along", with Brian Bennett of the Shadows.
He continued working in the London music business; among other successes discovering singer-songwriter Labi Siffre.