Formed in 1967 and scoring a string of extraordinary UK hit singles and a No 1 album with the still iconic Stand Up two years later, Jethro Tull's career remains unique in combining musical complexity with great tunes and a measured, literate and almost pantomimic absurdity in lyric and performance. It must rankle with pop historians that runners-up to the Beatles as Best Group in the 1969 Melody Maker poll were not Led Zeppelin but Ian Anderson's strolling players. That Anderson has been a multi-millionaire gentleman farmer for the past 20-plus years must also rankle - and, frankly, one must wonder, however welcome this rare foray into Ireland is, why he still feels the need to cavort around on stages.

Glimpsed in the barely-contained energy of My Sunday Feeling from Murray Lerner's 1970 Isle Of Wight Festival documentary, Tull's original formula was fresh and exciting. These days, however, a Tull performance stands or falls on how well it - and most particularly Anderson's voice - measures up to the original recordings. It is a quintessentially English exercise in Rourkes' Drift futility, but by golly they give it a go. While My Sunday Feeling and A New Day Yesterday revealed, floating above their musical muscle - and this remains a band of dazzling musicians - the strain in Anderson's vocal delivery, more recent material (pitched lower) fared better while perennial Bach (instrumental) novelty Bourree received a rightly thunderous response. A Tull show is a cerebral rather than emotional experience, and on that basis you pay your money and take your chance. Yet the evening's highlight was already taken in the moment when the genuinely engaging special guest act, American songwriter Willy Porter, deviated into Here Comes The Sun.

For all their qualities, spontaneity is no longer, if ever it was, in the realm of Jethro Tull.