Commuting through London

Hello London commuters, I've just got a new job (fantastic cycle facilities btw) and to get there I have to go from south of the river through to Kings Cross. South London is no problem, I generally cross at Blackfriars Bridge and go up Grey's Inn Road but I've tried a couple of different routes, however I always seem to get stuck in traffic in the city - there seems to be a lot of HGVs around too. Does anyone have any suggestions to get from Blackfriars to Kings X? I've looked online, but some real world suggestions would help my route I'm sure.

Thanks for your help!