Bilbo isn’t the only thing that feels like butter scraped across too much bread.

When the decision was made to expand “The Hobbit” from two films to three, there was always a risk the material would feel too stretched and if the strain was going to show anywhere, it would be in the middle section, “The Desolation Of Smaug”. And the strain does show, there’s no denying it.

“The Desolation Of Smaug” is the weakest of the five Tolkien movies to date, and its key flaw lies in its pacing. The first hour feels particularly awkward and jumbled together. The patchwork between the scenes originally shot and those shot later to expand the story to three films is particularly evident and it doesn’t help that the film begins with a flashback instead of picking up exactly where “An Unexpected Journey” left off. It’s scenes like that which baffle the most, because it’s not the decision to make “The Hobbit” a trilogy that’s causing the problem – it’s the seeming desire to make each film nearly three hours long.

However, we’re nowhere near the depths plumbed by the “Star Wars” prequels here and there’s so much to enjoy that you can almost overlook the other indulgences. From Mirkwood onwards, the film improves markedly and while not everything hits its mark, when it does, it’s jaw-doppingly spectacular.

The Mirkwood spider sequence is thrilling and wonderfully realised on screen and once we reach and breach the Lonely Mountain, the effects are nothing short of astonishing. Smaug himself is probably the most perfectly realised dragon ever to grace the screen, recognisably motion-captured from, and menacingly voiced by, Benedict Cumberbatch. Occasionally, some set pieces are allowed to overstay their welcome, such as the barrel escape which, while undeniably a fun sequence, seems to go on for at least twice as long as it should. The High Frame Rate continues to be a mixed blessing, making some of the Mirkwood scenes and later in Laketown look like television rather than a movie but it really comes into its own during the darker sequences, particularly the battle between the dwarves and Smaug.

While the film is at its strongest when its sticking close to the text, the additions and embellishments Jackson and his team are a bit more hit and miss. The sequences with Gandalf venturing to Dol Goldur add little to the film apart from slowing it down and sometimes providing an unwelcome break in a more interesting storyline. On the other hand, the addition of brand new character Tauriel is actually quite successful, and it’s good to see a strong, capable female character in these kinds of films. Yay equality! Unfortunately, she is drawn into the adventure because she falls in love, but at least her romance is interracial so, you know, still – yay equality! Evangeline Lilly acquits herself well and proves herself up to the task of matching Orlando Bloom’s returning Legolas for showy bow and knife fighting moves.

Martin Freeman is superb as Bilbo and his performance here and the character development is easily the equal of Elijah Wood’s Frodo in “The Fellowship Of The Ring”. The dwarves all get a little bit more to do in this film and start to gain more distinct personalities, especially Kili, Balin and Bombur, who has a laugh out loud moment with the barrels, but I still find Richard Armitage’s petulant and impetuous Thorin hard to like. It pains me to say it, but Stephen Fry’s Master of Laketown is also a little broad for my taste, veering a little too closely to his “Blackadder” performances than befits a film of this stature. I also still can’t shake the nagging feeling that Dori is, in fact, played by TV’s Mr Tumble, Justin Fletcher and that Ori isn’t played by his fellow CBBC alum Dan Wright (of ‘Big Cook, Little Cook’).

Individual parts of trilogies are difficult things to judge in isolation, especially when I have no idea how the third and final chapter will play out, retrospectively enhancing or diminishing “The Desolation Of Smaug” as it may. But for now, it remains a film which for two-thirds of its running time is a spellbinding, epic fantasy, the rest merely adequate. Maybe I’m just a bit jaded though – I took Mertmas with me to see it and he enjoyed it a lot. If Peter Jackson can keep a seven-year-old’s attention for a movie which lasts nearly three hours, he must be doing something right!