A new overtaking rule has been added to formula one's official sporting regulations for 2012.
Last month, the FIA flagged the forthcoming rule by announcing that drivers "may no longer move back onto the racing line having moved off it to defend a position".
The rule has until now been an unwritten one that was agreed and understood by the drivers, with the stewards empowered to issue penalties for questionable manoeuvres.
But from 2012, the actual regulations now declare: "More than one change of direction to defend a position is not permitted.
"Any driver moving back towards the racing line, having earlier defended his position off line, should leave at least one car width between his own car and the edge of the track on the approach to the corner," the rule goes on.