Here's a question: what film could not be improved with the addition of apes? You'll struggle to answer, believe me. I love Chris Nolan's Batman films but it's unarguable that they would be greatly improved with the addition of Detective Chimp (and imagine how much more fun his dreary Inception would have been if it had featured monkey mind assassins). Twelve Angry Men? Classic. Now imagine Twelve Angry Men And One Furious Baboon. You see? Already the thrills are leaping and shrieking off the page. The Apes Of Wrath? Any Gibbon Sunday? Orangs Are Not The Only Fruit? Conan The Barbary-ian? Whichever way you peel the banana, Apes = excitement.

So imagine my unparalleled joy when upon viewing the trailer to Matt Reeves's Dawn Of The Planet Of The Apes – the sequel to 2011's surprisingly solid Rise Of The Planet Of The Apes – I saw the sight that cinema has been awaiting since the Lumiere Brothers made the audience flee the oncoming train: that's right, fellow thrill seekers, an ape, on horseback, firing two heavy calibre machine guns AT THE SAME TIME. “This is an age of marvels!” I stammered, holding back tears “All the rest of this year's cinema is void...” It was quite the moment.

And, upon watching the film in its entirety, I can confirm that it is still a jaw-droppingly audacious sequence, but that what surrounds it is mostly hokum of the lowest order. Someone making this film knew how to deliver a fun-packed blockbuster, but it's as if they were outvoted at every turn by the enemies of joy. As a result Dawn..., though frequently engaging (apes, remember?), stumbles into the traps that have ensnared nearly every other recent Summer blockbuster: it's too long, too self-important and almost totally devoid of humour.

Following the events of the previous film, a speedily evolving band of apes – led by Andy Serkis' Caesar – discover the existence of a rag tag bunch of human survivors of the plague that nearly wiped out the human population of the earth. The existence of a traitor in the ape ranks threatens to destabilise the fragile peace that is established between the two races and a fight for survival ensues. Sounds simple enough, and good portions of the film deliver.

The apes themselves are never less than magnificent and Serkis's performance in particular is a masterclass in damaged nobility; every eyebrow twitch and armpit scratch skilfully emoted and motion captured to paint a complete picture of a world weary and just leader. It's a terrific performance. Indeed, it's the combination of special effects and superb acting that keeps the film watchable despite its running time. Toby Kebbell, who imbues Caesar's lieutenant, Koba, with menace and ferocity, is also worthy of a mention, and it's this aspect of Dawn... that nearly saves it: the special effects are so good that they nearly constitute... a Zaius Ex Machina!

I am so f*cking sorry about that one.

However it all goes to pot when the dreary homosapiens get involved. They try, bless them, but the script just isn't up to the task of making the human characters very interesting, to the point where I found myself in the strange position of wishing for my own species' extinction. Jason Clarke remains a likeable enough everyman, but Gary Oldman as Dreyfus, leader of the survivors, goes into his default position pretty much immediately - scrunching his face up and yelling in a manner that suggests he was having his lines dictated to him through a knackered ear piece. Compared to the apes the humans seem flat and one dimensional and it's their portion of the story that drags the pace of the film down to a flat footed lumber.

However, as previously mentioned, the whole sorry affair kicks up a gear massively when we get our first glance at Gorilla Warfare. The apes assault on the human compound is pulse racingly exciting stuff (although resolutely PG rated): massive explosions, monkeys carrying heavy weaponry and the once in a lifetime sight of an ape-eye-view from the turret of an armoured troop carrier. It's one of the few scenes that delivers the sort of bang-for-your-buck excitement that the trailer promised. Shaving Primate Ryan, if you will. The climactic stand off between Caesar and the ape traitor is also fantastically and vertiginously presented. All the effort that's gone into making the apes relatable and sympathetic pays off, resulting in what could have been simply a CGI smack down carrying a proper level of dramatic heft.

But, sadly, that leaves us with the rest of the film and its near complete lack of surprises. There are moments of inspiration – I certainly wasn't expecting a human/orang utan bonding moment over a copy of Charles Burns' Black Hole, for example – but they're scattered few and far between, with far too many predictable interludes to wade through to reach them. For a film concerned with tree-dwellers this film feels resolutely earthbound. I'm gibbon it the thumbs down. Still, any excuse to watch this again: