Lawyers used sheepskin as anti-fraud device for hundreds of years to stop fraudsters pulling the woo

Experts have identified the species of animals used for British legal documents dating from the 13th to 20th century, and have discovered they were almost always written on sheepskin, rather than goatskin or calfskin vellum.

Sheep deposit fat in-between the various layers of their skin. During parchment manufacture, the skin is submerged in lime, which draws out the fat leaving voids between the layers.

Attempts to scrape off the ink would result in these layers detaching—known as delamination—leaving a visible blemish highlighting any attempts to change any writing.