221B

Rule 221B by some is believed to be inspired by the Baker Street variation of the MC game. Whether or not this is true is difficult to say – Stovold's among others put forward a theory saying that it actually came out of a discussion between Mrs Trellis and the late Archdeacon of Oakham.

There are strong similarities – one or all four magenta stations must be involved in outset or arrival and spin coefficients play a major role. The differences are equally strong though – diagonals are not restricted but mandatory and the fifth magenta station, North Greenwich, has never been considered appropriate.

Generally, it is seen as very risky to attempt any Heathrow Terminal moves while Rule 221B is in effect.

---

Categories: A to Z