Missing Darwin notes returned to uni library

Two of Charles Darwin's notebooks containing his pioneering ideas on evolution and his famous 'Tree of Life' sketch have been returned anonymously after going missing for 21 years, Cambridge University Library says.

The prized documents were left on the floor of the university's library in a pink gift bag, with a typed note wishing a Happy Easter to the librarian.

The British scientist filled the leather notebooks in 1837 after returning from a voyage on HMS Beagle.

The notebooks were listed as missing in 2001 after they were moved to be photographed.