BluntM8 - lawyers working for the firms you describe are expected to work their nuts off for a good ten years if they want to stand a chance of partner. And I mean nuts - that's 8 til 8 five days a week, and then plenty to take home for the w/e. Sure, they get well paid for it, but it's very tough.
SFAC - if you've got a law degree that proves you can learn. You should be also be able to think, and express your thoughts in a clear, precise fashion on paper and verbally. With the correct preparation that will get you a long way. A mate who went Sea Harrier was a qualified barrister before he joined the RN.