Search london history from Roman times to modern day
A bit out of date, but this interactive map of step free London is very good
All the London railway stations :
Underground lines : London Overground (East London line)
AccessAble Access Guide :
Accessibility friendly : Yes, it is step-free. Ramps onto trains.
General description : See wiki
More comment : National Rail Map & Guide . Lifts to all platforms - no boarding ramps available or step / gap information available.