London Open - Rules of Play

From 2010, the London Open rules of play are the AGA-style rules, with the one exception that the illegal move rule is replaced by the EGF rule 4 below. The London Open Rules implements the second option for the rules of play in the EGF General Tournament Rules.

The following highlights the key points from the rules document:

  1. Komi in an even game is 7.5 to White. In a handicap game, White wins Jigo.
  2. Whenever a player passes, the player must hand a 'pass stone' to the opponent. This stone is added to the opponent's prisoners.
  3. It is illegal to play so as to recreate a previous board position with the same person to play (ko and natural situational superko).
  4. If an illegal move is made and if this is noticed within three moves, then the game must be unwound to the position just before the illegal move and play continues from that point. If the illegal move is noticed after three moves, the game just continues as it is.
  5. Play pauses after two consecutive passes. The players must then attempt to agree on the status of every group. If the status of all groups is agreed, then the players must ensure that White passes last. So if necessary, White must pass again and hand over another pass stone.
  6. If there is a dispute about the status of any groups after two consecutive passes, then play resumes on the clock, with the opponent of the last player to pass going first. The resumption can be repeated as many times as necessary with two passes causing the game to pause for an attempt at agreement on group status.
  7. If at the start of a resumption, both players pass (so making four consecutive passes in all) then the players accept that they cannot agree on the status of all groups. In this case the game stops and all stones remain on the board for counting purposes. Again the players must ensure that White passes last.
  8. The score is determined exacly as in normal territory counting i.e. place any prisoners into the opponents territory. Territory is defined as empty points surrounded by stones of the same colour. So eye points in seki do count as territory.


  1. Dame are worth one point each.
    a. Fill all dame before passing. Missing the last dame costs you two points.
    b. Play any dame within a seki that does not destroy the seki.
  2. Playing inside your own territory or your opponent’s costs nothing.
    So you can reinforce any potentially unsafe situation at no cost. However do this only when all dame have been filled.
  3. Bent four in the corner must be played out.
    Bent four is not treated in any privileged way. For example, if there are external ko threats that cannot be removed, then the fight continues. If necessary, this and any other special situations must simply be played out until the relevant stones are actually captured.
  4. Repeating positions are illegal.
    Situations such as cycling round triple ko are no longer treated as jigo. Playing a move to complete the cycle is illegal and Rule 3 would then be applied.
  5. Considerations about the last end-game ko can get complicated.
    For example, if the opponent plays dame instead of a real ko threat, just fill the ko and don’t play another dame.
  6. Resumption.
    Suppose you pass, your opponent passes, and while checking the status, your opponent challenges the status of a group. You must resume.

    First look for any needed re-inforcing moves that may have been missed on either side. Then look for any genuine dame and if none, just play a stone anywhere. If you do pass again, the game stops, and all groups on the board are alive!

Last updated Tue Dec 18 2012. If you have any comments, please email the webmaster on web-master AT britgo DOT org.