Re: Lost count...
so it'll only take an hour to drive across the middle of London
Depends on how fast your motorbike is and how close to death you want to be :-)
(I vividly remember riding across London on my power-restricted 125 Honda XL125 and having taxis overtake me on both sides on the bit of road near Hyde Park corner. It's the one and only time I've ever been terrified on a motorbike.. This was pre-M25 - not that I could have used that bike on the motorway since I was still a learner at that point. That bike regularly took me London-Leicester when I was a student there - even if it did take 4 hours and involve several stops so I could put my hands near the engine until the feeling came back in my fingers.)
 I lived in Barnet, oldest brother lived somewhere sarf of the river. It might even have been Croydon. I never did that ride again on that bike..