This Friday I have decided to give you a mystery object that I have to deal with on a regular basis. Something that I get more enquiries about than anything else. Do you know what this is?
Your only clues are that they come in a range of sizes and they are often found on the South Coast of England by walkers.
As usual, answers below – I will do my best to respond to questions, but I have a submission deadline looming for corrections on a paper, so I may be a bit tied up. Good luck!