In message , Richard J.
writes

Baker Street this afternoon, eastbound Circle line. Judging by how long I
waited and the number of people on the platform when I got there, I reckon
there was a 10-minute gap in the service. Nothing exceptional about that,
though it should have been 4-5 minutes.

Why do you think that the circle line runs at 4-5 minute intervals?

--
Paul Terry