Historical note: Prior to the release of the Holland Park 2000 rulseset, there were only four magenta stations valid for play under the Baker Street rules.
Prior to the Loop Amendments of 1973, the [Hammersmith Harmonic]? was a significant contributory factor to the severity of the Hainault and Amersham / Aldwych loops and certainly did nothing to help the notorious Mornington Crescent loop.
[SM]