An English pianist and organist, Hopkins recorded and performed on some of the most important British and American popular music recordings of the 1960s and 1970s, and is widely regarded as one of the most important session musicians in rock history.

Hopkins suffered from Crohn's disease since his youth and poor health and ongoing surgeries made it difficult for him to tour. This contributed heavily to his focus on working primarily as a studio player.

He started his musical career in the early 1960s as the pianist with Screaming Lord Sutch's Savages, which also included Ritchie Blackmore, founder of Deep Purple. He then joined Cyril Davies's R&B All Stars, one of the first British rhythm & blues bands.

He began his career as a session musician in London in the early 1960s and quickly became one of the most in-demand players on the thriving session scene there, contributing his fluid and dextrous boogie-woogie influenced piano style to many hit recordings. He worked extensively as a session pianist for leading UK independent producers Shel Talmy and Mickie Most and performed on albums and singles by the Kinks. His performances with the Rolling Stones were among his most memorable, notably on Their Satanic Majesties Request, Beggars Banquet and Let It Bleed. Hopkins also played on Jamming With Edward, an unofficial Stones release that was recorded during the Let It Bleed sessions. The 'Edward' of the title was an alias of Hopkins, derived from his outstanding performance on Edward, the Mad Shirt Grinder on Quicksilver Messenger Service's Shady Grove album.

In 1965, he played piano on the Who's debut album, My Generation, and recorded with most of the other top British acts of the time, including the Beatles. He also helped define the San Francisco sound, playing on albums by Jefferson Airplane, New Riders of the Purple Sage and Steve Miller Band. He briefly joined Quicksilver Messenger Service and performed with Jefferson Airplane at the Woodstock Festival.

In 1967, he joined the Jeff Beck Group, playing on their influential albums Truth and Beck-Ola.

Hopkins was added to the Rolling Stones live line-up on the 1971 Good-Bye Britain tour, as well as the notorious 1972 North American Tour and the early 1973 Winter Tour of Australia and New Zealand. He is featured heavily on the classic 1972 Exile on Main St. album. He started to form his own band around this time, but decided against it after coming off the Stones tour. He had planned on using Prairie Prince on drums and Pete Sears on bass. Hopkins failed to make the Stones' 1973 tour of Europe due to ill health and, aside from a guest appearance in 1978, did not play again with the Stones live on stage. He did manage to go on tour with the Jerry Garcia Band during 1975. He also continued to record with the Stones until 1980, and on solo records of members of the Stones up to 1991.

In 1973, Hopkins released his second solo album, The Tin Man Was a Dreamer, which included guest appearances from George Harrison (credited as George O'Hara), Mick Taylor of the Rolling Stones and Prairie Prince, who was later the drummer for the Tubes. A third album, No More Changes, followed in 1975, and he recorded a fourth album, Long Journey Home, which remains unreleased.

Hopkins lived in California for several years and continued to record in San Francisco. He died in 1994, aged 50, in Nashville, Tennessee, of complications from intestinal surgery.