Playing holes out of sequence

[woofers]

In a competition a group started on the 1st, and after playing the 8th, presumably due to speed of play and seeing the gap between the groups in front of them, decided to cut across from the 8th hole to the 11th and then after completing the 18th, played the 10th and then the 9th. The layout of the course has the 1st and 10th tees, and 9th and 18th greens close to the clubhouse. They did not interfere with the pace of play of any other groups.
Rule 5.1 states that a round is played in the order set by the Committee. In the absence of any statement to the contrary presumably this would be sequentially 1 to 18?
It would seem that the group have breached rule 5.1, but there is not a specific reference to a penalty for this, so under which rule would any penalty be applied?

 

[salfordlad]

See Rule 6.1b(2). In stroke play, playing from the wrong tee gets the general penalty and if not corrected before making a stroke to begin another hole, the player (here all players) is DQed.