The release of a new Laura Marling album is always noteworthy, and not least because she's become one of the best songwriters that England can claim as its own, even if she's since relocated to Los Angeles. Her music has been moving down an increasingly darker path since debut Alas, I Cannot Swim was released five years ago, and as her career has flourished, so has her ambition. Her new album opens with a 16-minute medley split into four songs, and by the end of 'Breathe', it becomes apparent that she's no longer writing for a pop audience. She had already left her competitors eating her dust by the time she released I Speak Because I Can in 2010. Marling's had two high-profile relationships in the time she's spent in the public eye - with Noah and the Whale's Charlie Fink, and Marcus Mumford of Mumford and Sons - and her new record finds her in surprisingly confrontational form. On 'I Was An Eagle', she declares her intent not to be "a victim of any man who could get his dirty little hands on me," while she's closed herself off altogether on lead single 'Master Hunter': "I cured my skin so nothing gets in / Nothing as hard as it tries." That song set the tone for Once I Was An Eagle as a whole - the mood is one of introspection, and there's an air of sparseness to some of the material on the record.

There's quite a lot of material there, too, with Marling's latest clocking in at 63 minutes and featuring no less than 16 songs. That's a whole 22 minutes longer than her last effort, 2011's A Creature I Don't Know, but it doesn't feel like that in the slightest. An album as long and inward-looking as this could easily have ended up dreary and one-note, but it's a rather more diverse affair than that. Those looking for a taste of Marling's sound at its most fragile will enjoy 'Little Love Caster', but whilst being a good song, it's swept away by 'Devil's Resting Place', a much more powerful song, which leads into a violin interlude to close the first half of the album. Despite much of the record being cut from similar, mid-tempo cloth, the sheer variety of instrumentation sweeps it along; there's a surprisingly upbeat feel to the organs and gentle percussion of 'Where Can I Go?', which makes Marling's delivery all the more poignant as she sings, "Late at night he'll come to me and he'll tell me I'm alone / Don't you think I don't already know?"

The defensive tone of many of the lyrics on the album gives the collection an emotional rawness that is more palpable than ever before. Marling bares her soul not because she wants to, but because she has to - or so it would seem. She's been hurt in the past, and while some will see her outlook on her new album as being overly self-pitying, it takes guts to be as honest as she is on songs such as 'Once' and 'When Were You Happy? (And How Long Has That Been?)', and the fact that her lyrics remain as relatable as ever mean that she only stands to gain an audience from her most personal set of songs yet. Optimism is hard to come by on an album like this ("Thank you naivety for failing me again" is her kiss-off on closer 'Saved These Words'), but on a musical level, Marling is at a peak of confidence, and it wouldn't be too remiss of me to suggest that Once I Was An Eagle is her best album yet; better individual songs may lie elsewhere, but her new record's cohesive nature makes it much more of an adventure than what came before. Why just coast when you can learn to soar?