The man is accused of nine offences of indecent assault against children and eight of committing acts of indecency against children between 1973 and 1986.
He has denied all the charges and the court heard he told police he would be too embarrassed to expose himself in public due to having an "unusually small penis".
"The prosecution say this defendant is an entrenched paedophile. It would appear that he cannot help exposing himself to young people or getting himself into situations where he can sexually touch or assault them." said Sean Brunton, prosecuting at Plymouth Crown Court.
The court heard that Sheryn, of Plymouth, Devon, was so well known in the villages where he lived that he was nicknamed "The Flasher".
"He told police he would not have exposed himself because he has an unusually small penis and he would not want anyone to see it." said Mr Brunton.
According to Sheryn, the first complainant had made her allegations up and persuaded others to lie. He also denied ever flashing to children.
But the court heard that Sheryn had convictions for exposing himself "as far apart" as 1981 and 2014.
Sheryn has published numerous books on excavation [link to amazon] selling hundreds of copies all over the world. He has also given multiple lectures on the subject.
For now, Sheryn has pleaded not guilty to nine offences of indecent assault against children and eight of committing acts of indecency against children between 1973 and 1986. He has also denied attempting to indecently assault a boy.
The trial still goes on. I will keep the post will be updated if anything new comes up.
Update: After a 5 day trial, Sheryn was found guilty on all counts after a female sex worker - whom he often visited - testified that he has a normal sized penis. Sheryn has now been jailed for 17 years and was found guilty for 18 crimes.