After a month of freakishly dry weather over Scotland, the heavens opened on Thursday just in time to soak more than 30,000 fans gathered at Hampden Park stadium to christen Neil Diamond's latest tour.

Perhaps it was these adverse conditions, or this grim cattlepen of a venue, but the 67-year-old New Yorker seemed on strangely lacklustre form for a man currently enjoying the biggest comeback of his career.

Diamond's critical and commercial standing has never been higher. He topped the album charts on both sides of the Atlantic recently with Home Before Dark, his second collaboration with producer Rick Rubin, who is credited with overhauling the singer's kitsch image. Appearances on American Idol and a sycophantic all-star ITV special also boosted his profile. Later this month he will play the Glastonbury Festival.

But surprisingly, given his long and successful career, Diamond is not a very dynamic performer. Shuffling around the stage in Glasgow, he danced stiffly and awkwardly during clomping tub-thumpers including Pretty Amazing Grace and I'm a Believer, a song he wrote but the Monkees made famous. He is sometimes compared to Tom Jones, but Diamond's manly bellowing lacks the Welshman's caveman sexuality and self-mocking humour.

His voice remains a mighty instrument, growing more ripe and textured with age, like a fine cheese. But his booming delivery, usually accompanied by his default furrowed brow and frozen stare, was remarkably devoid of emotional nuance. At times he looked embalmed. Or possibly constipated.

Rubin may have helped to strip away the overblown kitsch that was once Diamond's Achilles' heel, but an unwittingly comic pomposity still defines the singer's performance style. The towering self-pity anthem

I am... I Said, in which the singer defiantly declares his existence to an uncaring universe, including a cruelly uninterested chair, is one of his best and biggest hits. But his solemn intonation of this absurd lyric in Glasgow was still difficult to take seriously, recalling Star Trek veteran William Shatner's hilariously po-faced albums of spoken-word cover versions.

Diamond wore a series of expensive-looking shirts during the two-hour set but never came close to the rhinestone-studded flamboyance of his 1970s heyday. During You Don't Bring Me Flowers, he perched at a mock bistro table, sipping mock wine and wallowing in mock melancholy.

These were feeble nods to the grand theatricality of his past in an otherwise disappointingly austere show.

Ironically, despite Diamond's post-millennial rebranding as a cheese-free icon of soulful sincerity, this soggy and joyless venue could definitely have benefited from a little more spangly escapism.

In fairness, Diamond's flair for writing populist karaoke classics cannot be denied. Even as the rain turned torrential in Glasgow, the stirring fanfares and crashing peaks of Sweet Caroline and Cracklin' Rosie provided an irresistible singalong finale.

Thunder and lightning shook the skies overhead, raising the real possibility that even the rain gods may be Neil Diamond fans. All the same, they helped to make this show a dispiritingly damp affair.

Glastonbury-goers, you have been warned.

On tour: next shows tonight and tomorrow, Manchester MEN Arena. Then Tues 10 & Weds 11, Birmingham NIA; Tue 17, Southampton Rose Bowl; Thur 19 & Fri 20, Cardiff CIA; Sat 21- Tue 24, London 02 Arena; Fri 27, London Wembley Arena.

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