It takes four songs for Bruce Dickinson to shout what everyone knows he is going to shout: “Scream for me, Birmingham!” For their 50th anniversary tour, Iron Maiden are not reinventing the wheel – they are, as ever, playing fast and intricate heavy metal. As ever, Dickinson spends much of the set on top of the backline, acting out characters, Steve Harris machine-guns the audience with his bass while playing his “galloping” lines, and Janick Gers, when not swinging his guitar around, sticks his left leg in the air and rests it on the stage side speakers. No idea why. But he always does it. And, of course, the song subjects are the contents of a 12-year-old’s head: the Battle of Britain (Aces High); crazy mental powers (The Clairvoyant); Satan (The Number of the Beast). You get the picture.

The one deviation from usual, Dickinson informs us, is that this is as near as Maiden get to a greatest hits show: the most recent song tonight, Fear of the Dark, dates from 1992. For the less committed, that is a good thing. Maiden have a tendency to be windy, and this format – their early songs were generally shorter and sharper – helps with that, though it doesn’t eliminate it entirely. Rime of the Ancient Mariner lasts nearly as long as a cross-channel ferry, and you can’t even buy duty free to pass the time.

Age is starting to show, too: Dickinson’s famous “air-raid siren” voice is still a thing of range and power, but it is more “car-alarm voice” now. And in this echoey, sweltering arena, some of the complexities of the sound are lost (the mix leaves new drummer Simon Dawson so low at times that one loses the beat; guitar solos are mixed so high the rest of the band sometimes disappear behind them), which is frustrating.

But what an institution: a band whose career has been constructed absolutely on their own terms without a single compromise, something few artists can manage. And, of course, Birmingham screams for them, long and loud.

• Iron Maiden tour England and Ireland until 30 June