After going through this thread, I felt compelled to respond. I'm Dave, Evan's co-conspirator in this suspicious record-setting A-Z challenge. Although Evan's post seemed to give some more credibility to our record, I thought I'd add a few thoughts.
As Evan wrote, both of us are quite familiar with London and the Tube. Evan and I planned and recorded our A-Z challenge meticulously, and we are hoping to return in March to attempt a proper Tube Challenge (if anyone would like to volunteer as a timer, please help 2 Americans out

Some of the suspicions arose after people read our rather blase write-up of the record. I'll be a good friend and pin the blame on Evan for that. I will say, however, that yes, we did "run briskly between changes." If we hadn't, we never would have caught the Baker Street-bound Metropolitan line train at Ickenham, and we wouldn't be having this conversation right now.
I believe sub-5 hours can be done, but only if you run more briskly than we did
