I'm not familiar with the differences between the US and the UK; here in the US, hard work won't get you to the top, but it is a required part of the formula. It seems to me that 'hard working' is just one component of a personality type that lends to success. Risk-taking and a drive to assume more responsibility are part of it.
Of course, if you are poor, a woman, or a minority, in the US, the deck is stacked against you. It is significantly more difficult for you to 'get to the top'. Unfortunately, because we invest so little in the education of our poor, by the time they grow to become their own advocates, they are often so far behind that there is little hope of ever catching up.