For any age group, weight, gender, bmr? Interested as I will need to manage this too.
The short answer is generally yes, for most people irrespective of weight, sex etc. The reason is the capacity of the human liver, specifically to store glycogen, doesn't vary much between us human beings. I can't recall off the top of my head but I think it is around 100-120 grammes of the stuff.
The reason liver glycogen is important (more so than muscle glycogen although that is handy if you are looking for a big sprint finish) is that it impacts your central nervous system and glucose is important for brain function. If you run out you may find yourself involuntarily doing some strange thing like veering off the road into a ditch (bonking or summat) until your body can find another source of glucose either through eating something or internally. It can mean your ride is over though which would kind of suck.
So, eat fairly regularly. How quickly you burn through your glycogen stores depends on the intensity of your riding (the higher it is the quicker it gets depleted.) No need to get overly paranoid about it though if you are maintaining a pace you are comfortable with.
Finally the preferred source of topping up liver glycogen is fructose so if you look for anything with a high fructose content (like dried fruit, fig rolls, errrrrr, jammy dodgers etc) you will do yourself a favour.
Good luck to all doing Ride London and I will see you on the day. I will be the one going rather slow but looking fine
. But, for the OP, could make the difference between getting home fairly comfortably or struggling after about 50-60 miles; and all because of a little cake fetish. 
