Nope not in the slightist.
But generally the Old Bill just tell you to change it sometimes they will give you a producer type thing which you have to get stamped at an MOT station to say you have changed it to a regulation size one.
The absolute worst they can do is give you a £30 fine.
I've never had a fine and only once had to take it to an MOT station.
If you do get pulled for it just asked them if they have got anything better to do and if they have caught any real criminals today! They love that, makes them Laugh everytime
Rich