I was in the Ashmolean in Oxford yesterday and I stumbled upon these absolute gems!
These are associated but not confirmed as a series of first oil sketches painted by Frederic Lord Leighton during an early summer 5 week stay on the Island of Capri in 1859. He was influenced by his friend Giovanni Costa.
The above painting and detail is my favourite, it stopped me dead in my tracks as I was trying to find a route back to the Egyptian and Nubian department. Going by size and style I'd like to think these are plein air paintings, according to the museum they were studies not intended to be seen by the public.