The incomplete charge is between £4.60 and £6.70 depending on whether it's peak or not, I think.

I can't say I agree with the location issues of the LCY Oyster readers. They are just before the red line delineating the entrance to the compulsory ticket area. There is also a woman there most mornings inspecting people's cards and telling them to touch in/out.

Somewhere around 3% of TFL journeys are incomplete, which is a tremendously high number. I wonder though are they including Travelcards on that — if you touch in or out within the zones of a Travelcard on your Oyster but not at the other end, there is no charge. This is partially a legacy thing because Travelcards on Oyster were valid before pay-as-you-go at a lot of stations (full PAYG within the zones is only around since January 2010) and partially to allow for people using Travelcards on Oyster plus a Boundary Zone ticket on a fast train.