I have to say that I agree with Anna here that sexism is not the main thing to blame. I worked in London for a long time, both in the public and private sector (city job); I regularly performance assessed people (or assisted in the process), and in my experience sexism is not more pervasive than, say, racism. I have seen, say, non-drinking men being discriminated in the City much more than women!
If you were good you are good - male or female did not matter. Actually, in some cases (e.g. a particularly public or senior appointment), being a woman was an advantage, as organisations in general like to be seen promoting women to high places.
The gap IMO is more on the practical aspects already mentioned in this thread - the choice of going P-T after mat leave or whatever. Even women who could easily pay for childcare 24 hrs a day still chose to work shorter hours. Even if their DH was happy to be a SAHD, how many wold really give up the chance of being a SAHM or the main carer? I only know of one woman in RL who has gone down that route and the discussions I see on mumsnet seem support this view.
So before blaming men - I would like someone to calculate the average women salary once you take into the account the childcare hours they do on top of their jobs. Probably impossible, but I am pretty sure that the pay gap would be much smaller.
If we want to become more Scandinavian - well as parents we have to bring up our boys and girls to think in that way. And comparing to the previous generation, I believe we are doing a better job, and I hope the trend continues...