London: Two notebooks of British naturalist Charles Darwin stolen from Cambridge University library in 2001 have been returned with a note wishing the librarian a Happy Easter.
The notebooks with the 19th-century scientist's 1837 'Tree of Life' sketch was found in the library in a pink gift bag, AP reported.
The notebooks went missing two decades ago after being removed for photographing.
Failing to find them despite searching the library's collection of 10 million books, maps and manuscripts, the notebooks were declared stolen in October 2020. Later an international hunt for the books was launched with the help of Interpol.
The books valuing at millions of pounds reappeared on March 9 in a public area of the building outside the librarian's office not covered by surveillance cameras.
They appeared undamaged as wrapped in cling film inside their archive box with a note that said, "Librarian Happy Easter X".
Returning from his voyage on HMS Beagle around the world, Darwin filled the books with ideas on evolution for his future work "On the Origin of Species".
Jessica Gardner, the University's director of library services, expressed great relief at the return of the books.
She said the notebooks would take their rightful place at Darwin Archive in the library alongside the archives of Sir Isaac Newton and Professor Stephen Hawking.
The notebooks will be on display for public viewing as part of Darwin exhibition at the library.
Cambridgeshire Police reportedly would still continue probe into the missing of the notebooks.