A month later the band started its Friday residency at the Marquee as Jethro Tull. The band became a fixture in London's music scene and their image, headed by Ian Anderson's emblematic figure playing flute with a leg up and dressing like a beggar, made a lasting impression on the London hip.
Jethro Tull played their last gig at the Marquee in November 1968, two months after the release of their debut album This Was. The album foreshadowed Tull's eclectic mix of rock, jazz and English folk. While many bands were experimenting with classical and jazz oriented sounds, only Tull was zeroing in on what was blatantly British (a forte established by The Beatles), creating an atmosphere that summoned up the ghosts of Blake and Willy the Shake.
Early the following year, Tull began working on what would prove to be, for many fans, the group's magnum opus, Aqualung. Anderson's writing had been moving in a more serious direction since the group's second album, but it was with Aqualung that he found the lyrical voice he'd been seeking. Suddenly, he was singing about the relationship between man and God, and the manner in which organized religion separated them. The blues influences were muted, but the hard rock passages were searing while the pastoral folk influence provided a refreshing contrast. And everybody, college prog-rock mavens and high-school time-servers alike, seemed to identify with the theme of alienation that lay behind the music. Aqualung includes the stylized liner note: "In the beginning Man created God; and in the image of Man created he him . But as all these things did come to pass, the Spirit that did cause man to create his God lived on with all men: even within Aqualung. And man saw it not. But for Christ's sake he'd better start looking." Ironically, Aqualung is one of the few Jethro Tull albums where the lyrics are not printed, despite the fact this is arguably the album where the lyrics mattereth most.