The Rat and the Pencil.

No, its not a weird pub where sneaky rodent featured Bobbies hang out.
Its a story told to me years ago while young in service.
Police Constable from a road traffic motor cycle department is giving evidence at court in a reckless driving case.
PC " I followed the defendant for several miles your worship. He was riding a high powered motor cycle along a single carriageway road which is divided into two lanes, one in each direction, by continous unbroken double white lines. The defendant refused to stop and in fact drove at speed exceeding the limit for the road, overtaking slower moving vehicles and by doing so contravened the double white lines on several occasions. When he eventually stopped he denied both that he was in fact speeding and also that he had contravened the double white lines. He was therefore reported for the offences."
Defence Brief. " What speed exactly is it that you say my client was doing officer?"
PC. " I cannot say exactly your worship as the speedometer on my motorcycle had broken and I was in the process of returning it to the garage when I spotted the defendant."
DB. " So you cannot say with any accuracy that he was in fact speeding, can you officer?"
PC. " Your worship, I have been a traffic officer for more than 10 years and during that time I have been caused to exceed the speed limit numerous times while driving a variety of police vehicles. Because of this experience I would estimate that the defendant was doing between 80 and 90 mph in a 60 mph limit."
DB. " So you consider yourself a good judge of speed because of this experience do you officer?"
PC. " I do your worship."
DB. Picks up a pencil from his desk and throws it across the courtroom." How fast would you say that pencil was going then officer?"
PC. Deadpan. " I couldn't say your worship. I've never ridden a pencil before."