Of course the difficulty here is that, as with speeding, the allowance over the specified time will be seen as a "right" and the prosecution of minor transgressions above that allowance will be seen as "harsh".
With speeding, the Association of Chief Police Officers (or whatever they now call their organisation) issued guidance to say that speeds up to (limit + 10% +2mph) should not be prosecuted.The idea was to prevent frivolous challenges to the accuracy of measuring equipment from clogging up the courts. This meant that normally, speeds of up to 79mph (in a 70 limit) would not be punished. The result of this is that people travelling at 80mph and prosecuted now bleat that "I was only 1mph over the 'limit'" . Er...no. You were travelling at 10mph over the limit.
So it is with this. The ten minutes will become a "right" and people overstaying by 11 minutes will bleat that they have been penalised for just a one minute transgression. As they say, "Give them an inch and they will take a mile".