Like, as if you need an excuse to get out on your bike today...
There is an 'afterworker' ride starting at 18:30 from the Needle on the south end of London Bridge. Next to Evans bike shop. Route is towards central London. I'd hazard a guess at a stop for hops-flavoured water.
Feel free to add to the thread for any other areas, 'cos I know there is life north of Hyde Park.