Why is football knowledge measured by the offside rule?
The row over remarks made by Sky Sports presenters Richard Keys and Andy Gray about female assistant referee Sian Massey centres on the offside rules. But why is the offside law such a benchmark of football knowledge?
If you Google "explaining offside rule to women" you will find a widely circulated "amusing" explanation about two women in a shoeshop, having forgotten their purses, battling for the same pair of shoes.
It might not raise too many smiles among female football fans. But it's a reflection of the widely held belief that the offside rule is something that is not really easily understood by those uninitiated in football.
"It's the old joke about moving HP sauce bottles around the kitchen table," says Jeff Winter, former Premiership referee.
As written in the FA's Laws of the Game, Law 11 on offside is fairly brief at about 200 words.
"A player is in an offside position if he is nearer to his opponents' goal line than both the ball and the second-last opponent," the law says.
It says a player is not in an offside position if he is in his own half, level with the second-last opponent or level with the last two opponents.
It's not an offence in itself to be offside, but it is if the player is "interfering with play, or interfering with an opponent, or gaining an advantage by being in that position". You can't be offside directly receiving the ball from a goal kick, a throw-in or a corner kick.
Sound fairly simple? Apparently not in the minds of some fans and pundits.
"It's almost a joke - do you know the offside rule?" says Amy Lawrence, a football writer for the Guardian and the Observer. "It's the immediate [barometer] for how you judge someone's football knowledge. It isn't that complicated. If you wanted to know about it, it wouldn't take that long to figure it out."
Of course, as any fan of the game knows, Law 11 has plenty more to it than that.
What exactly is interfering with play, what is interfering with an opponent and what is gaining an advantage?
The FA's rulebook offers a further 500 words of explanation on the definitions and 13 helpful diagrams.
The 13th, which shows player C being in an offside position when the ball is first played forward, is particularly instructive. Player B, in an onside position, receives the ball and plays it back to C.
The so-called "phase one and phase two" aspect of the offside law can leave many struggling to understand.
"I'm not sure I do," jokes Winter. "They have not made it easy for the punter to understand now.
"Brian Clough said if you are on the pitch you are interfering. Phase one and phase two has made it very difficult."
The interpretation of the law has evolved steadily over the years, forcing the hardcore football fan to make efforts to keep themselves up to speed.
"Football rules are tinkered with on a relatively regular basis. You should read the rulebook every season," says Lawrence.
"There is always a grey area. For all anyone says they are an expert on it, it is still something that can be vague. I feel sorry for anyone officiating, trying to get it right all the time."
It might seem unfair to some that a law with such nuanced interpretation should be such a benchmark, but it remains a classic jibe.
The rule on what constitutes a foul throw perhaps does not contain as much meat as offside. Law 11 is easily parodied, as in this John Cleese video on YouTube.
In some other sports there are rules at least as complicated that are not equivalent badges of honour. Rugby Union's own law 11 on offside eats up considerably more paper and there are fans who will happily admit they don't fully understand it.
When England cricketer Graham Gooch was once given out for handling the ball while in play, there will have been a fair number of fans in the stands baffled for a few moments.
In football, the essence of the offside law is not knowledge but fine judgement. An attacking player who is distracting a defender but does not receive the ball can be adjudged offside, but what constitutes distraction? For the official, passing the pub-level knowledge test is not enough.
"Knowing the law and the rules is one thing. Practically implementing them is totally different," says Winter. "There is far more to controlling a game than perfectly answering questions but it's a stereotypical aspect of football - they say 'Do you know the offside law?'"
Even after multiple-angle analysis afterwards in a TV studio an offside decision can be impossible to clear up.
But for Massey, the big offside decision of the match hinged on a defender being level with an attacker.
And she got it exactly right.