Missing Charles Darwin notebooks returned after two decades

April 5 (UPI) -- A pair of Charles Darwin's notebooks that have been missing from the Cambridge University Library for more than two decades have been returned, the library announced Tuesday.

The notebooks, which include Darwin's 1837 Tree of Life sketch, were dropped off in a bright pink gift bag and stacked in plastic wrap by an anonymous person on March 9 along with a note that read:

"Librarian

Happy Easter

X"

The bag of notebooks was placed in a public area outside of the librarian's office on the fourth floor and did not show "obvious signs of significant handling or damage" since they disappeared in January 2001.

The notebooks were believed to have been misplaced for many years until librarian Jessica Gardner made a public appeal for their return in November 2020.

"My sense of relief at the notebooks' safe return is profound and almost impossible to adequately express," Gardner said. "Along with so many others all across the world, I was heartbroken to learn of their loss and my joy at their return is immense."

Police said that an investigation into the disappearance of the notebooks is underway, and Gardner noted that security at the library has increased in the decades since they were lost.

"The building has transformed significantly since the notebooks were first reported as missing," she said. "In the last 20 years, this has included completion of new high-security strong rooms, new specialist reading rooms and a range of additional security measures."

Cambridge University Libraries will put the notebooks on display as part of a free exhibition called Darwin in Conversation beginning July 9.