Bob Dylan made a stop on his Never Ending Tour in Cardiff's Motorpoint Arena last Thursday. Even though the tour name hasn't changed since 1988 this current leg is in support of his latest release, his love letter to the classic American songs of his youth, Shadows in the Dark.

The Arena was packed with fans of all ages. But, whether they were millenials or over-the-hills, anyone caught trying to take a snap of their icon or even a selfie with their iPhone was hunted down by the flashlight-wielding wardens, who paraded like so many harassed teachers trying to police a class of cunningly choreographed school children.

As soon as one naughty boy or girl broke ranks to fire off their flash a warden would race toward them brandishing their torch so as to ruin any chance of a good photo. At the same time anywhere between 20 and 200 other fans would start snapping while the warden's back was turned. A brilliant ploy and I'm sure all 5,000 strictly seated ticket holders got a chance to take a pic by the end.

And perhaps that should be enough: taking a photo of a living legend. Just seeing the man who wrote Like a Rolling Stone, Mr. Tambourine Man, The Times They Are a Changin' and Make You Feel My Love should be enough, shouldn't it?

As long as you don't honestly expect him to sing any of those songs on stage.

And why should we? Apart from Make You Feel My Love, made far more famous by Adele's 2008 cover of it, all those hits were written by 1965, before young Bob was even 25 years old. Dylan, now 74, wants his modern Music to be loved by his modern fans - fans like me, who know the 60s and 70s material is classic but love his retro-active return to roots. My step-father is of the old guard. He loves the brilliant new material but is tied in time to the Best of Bob days.

So when Dylan finally launches into an encore of Blowin' in the Wind we should all celebrate - unless it takes two verses to work out which song he's singing.

The problem isn't that he can't sing any more. The problem is that you can't hear what he's singing. The great poet of popular music has bad diction.

The odd thing is that although he treats his own material with such disregard, he is close to reverential in his interpretations of the Great American Songbook repertoire from his latest album. The band, whose post-rockabilly grooves play fast and loose with the Dylan originals, are a tight, concise jazz quintet when backing crooner Bob through classics like Autumn Leaves and What'll I Do? Suddenly we recognise the melodies, even to the songs we've never heard before. The lyrics are intelligible and Dylan holds out notes with control and finesse. If only one of the greatest lyricists of our time could treat his own words with such care.

So who leaves a 21st century Bob Dylan concert happy? Insert your own punchline here.