Aqualung

Most of the album was recorded in December 1970 at Island's new Basing Street Studios, with some re-recording in February 1971 after a European tour. Two tracks dated from earlier in 1970 at Morgan Studios. It was Jeffrey Hammond's first album as bassist, after Glenn Cornick was fired, John Evan's first as a full member, and the last with drummer Clive Bunker. Anderson said the larger Basing Street studio felt horrible, cold and echoey, while Led Zeppelin were working on their fourth album in the smaller room. He had considered hiring a producer, discussed it with George Martin, and concluded the band should carry on producing with Terry Ellis. Dee Palmer arranged the orchestral parts.

The idea began with photographs Anderson's wife Jennie took of homeless people on the Thames Embankment. Side one carries the title Aqualung and side two is called My God. Critics called it a concept album and Anderson consistently denied it, saying later that he wrote Thick as a Brick as a spoof of exactly that. "Cheap Day Return" was written after he visited his critically ill father, and "Lick Your Fingers Clean" was left off and reworked as "Two Fingers" on War Child.

Burton Silverman's watercolour on the cover was commissioned by Terry Ellis for a flat fee of $1,500, and the original front and back artwork has gone missing. The album reached 4 in Britain and 7 in the United States and has sold over seven million copies, the band's best. "Hymn 43" was the first Tull single to chart in America, at 91. Ben Gerson of Rolling Stone praised its fine musicianship, and Sounds called it the band's finest work. Iron Maiden covered "Cross-Eyed Mary" as the B-side of "The Trooper". Steven Wilson remixed it for a 40th anniversary edition in October 2011. Locomotive Breath and Aqualung are the two songs the band has played most in concert.