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IceColdUK: Checked on this one today, but the cache had gone. Sorry, but time to archive. [:(] Thanks to everybody that found it, anybody that had a go at the puzzle, and of course, to everybody who joined in with the cooperative phase.

To explain the puzzle:

The 19-character key for the cooperative game was "IMSORRYIHAVENTACLUE", giving moves from...
- Stratford (I -> 9 stops) to
- Oxford Circus (M -> 3 stops - not 13!) to
- Marylebone (S -> 9 stops) to
- Elephant & Castle (O -> 5 stops) to
- Old Street, etc.

For the second game, the key was "HUMPH" giving moves from...
- Knightsbridge (H -> 8 stops) to
- King's Cross St. Pancras (U -> 1 stops) to
- Euston (M -> 3 stops) to
- Old Street (P -> 6 stops) to
- Kennington (H -> 8 stops) to
- Mornington Crescent



Mornington Crescent

A cache by IceColdUK Send Message to Owner Message this owner
Hidden : 8/12/2011
3.5 out of 5
1.5 out of 5

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Geocache Description:

The cache is not at the posted coordinates. This is a puzzle to celebrate the king of strategy games, Mornington Crescent. Key to the game's popularity has been its regular inclusion (since 1978) in the Radio 4 panel show, "I'm Sorry I Haven't A Clue".

Mornington Crescent

NB. Although this cache was originally designed for cooperative effort, there is still a puzzle to be solved ... made somewhat easier, if you can find the right notes in the logbook!

Misguided sceptics claim that there are no rules to Mornington Crescent. I can assure you, this is not the case. In fact, the rules really are quite straightforward, and to illustrate, I'd like us to analyse a recent championship match, move by move.

To simplify things slightly, I've chosen a text book game that adhered to the Circle Line Concord, i.e. conventional rules applied, but the playing area was restricted - in this case, to tube stations in central London.

Like all accredited tournaments, the main reference was Stovold's. For this particular event, the following additional boundary regulations were stipulated by the Rules Committee:

  1. The playing area comprises Zone 1 of the London Underground, plus those exceptions stated below. [As the name implies, the Circle Line originally provided the outer limits for this variation, but nowadays this is more often extended to the Zone 1 boundary.]
  2. Current station and interchange closures apply. [This encourages more varied gameplay, and for this tournament, ruled out a number of the more prosaic strategies, such as the Blackfriars Bridge Defence.]
  3. Stratford (in Zone 3) is in play for the 'opening' only. [This relaxation of the rules was to celebrate the inclusion of Mornington Crescent in the 2012 Olympic Games. Hint: It would be foolish not to open with Stratford!]
  4. Kennington, Oval and Stockwell (all in Zone 2) are in play. [This is a common rule amendment in this form of the game, allowing for useful manoeuvres such as the Stockwell Reverse Platform Switch.]
  5. Mornington Crescent (also in Zone 2) is in play. [Obviously!]

Unusually for a championship event, the committee also applied the 1953 Trumpington Variation. [This allows a station to be revisited unless, of course, the move results in an adverse triangulation.]


  • N.F. Stovold's 'Mornington Crescent: Rules and Origins' - out of print.
  • Transport for London Tube Map (April 2011) - here.
Stovold’s ’Mornington Crescent: Rules and Origins’

Stovold's 'Mornington Crescent: Rules and Origins'

The purpose of the cooperative phase was to bring everybody up to speed on the rules of Mornington Crescent by replaying the moves of the chosen game. The challenge was completed by 15 Geocachers in little over a day and a half - only slightly longer than it took to actually play the game in the tournament. As suggested in the notes above, the game opened at Stratford. The 19 moves that took us to Mornington Crescent were as follows:

Stratford -> Oxford Circus -> Marylebone -> Elephant & Castle -> Old Street
-> Stockwell -> King's Cross St. Pancras -> Aldgate East -> Edgware Road -> Victoria
-> Green Park -> Baker Street -> Embankment -> Monument -> Bank
-> Waterloo -> Piccadilly Circus -> Embankment -> Charing Cross -> Mornington Crescent

For the record, the rules of the cooperative phase, the moves suggested and my commentary for the game are on my website - here. (None of this is required to solve the puzzle!)

The next step is to test your understanding of the rules of Mornington Crescent. The notes added by the 'co-op team', particularly the later ones, may help...

In the same event, another thrilling match climaxed with a dramatic five-move finish from the seemingly hopeless position of Knightsbridge. This innovative endgame has earned its place in Mornington Crescent lore, and was named a "Humph", in honour of the much-loved former chairman of ISIHAC.

Now, both of these games also adhered to the little-known IceColdUK Geocaching Principle (2011). In truth, this variation is far too restrictive to become part of the standard rules, but when applied, it does allow advanced players to demonstrate their puzzle solving ability and navigational skills. If you can understand the Principle, you should be able to follow the moves in the first game, and name the four stations between Knightsbridge and Mornington Crescent (A-D) in the second.

Using a familiar conversion, the cache can be found at:
N 51° 18.XXX W 000° 38.YYY
where XXX = (15*(A+B)*(C-D))-2
and YYY = (3*(-A+B)*(C+D))+7


Congratulations on the FTF to Kermit&Co, Miss-P and colincactus.

Additional Hints (Decrypt)

[Puzzle:] Rnpu tnzr arrqf n "xrl". Gur xrl jvyy qrgrezvar ubj znal zbirf gnxr lbh sebz n fgneg cbvag gb Zbeavatgba Perfprag ... naq fbzrguvat nobhg gubfr zbirf.
[Cache:] Gjva gehaxf.

Decryption Key


(letter above equals below, and vice versa)



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