The Dell was built in 1872 as a large house, in Grays, on the instructions of eminent naturalist Alfred Wallace. It was one of the earliest houses in Britain to be built in concrete. Courtesy of Wallace, there are plans and drawings of the house in the Natural History Museum, and the property bears a plaque with his name. There is a link to the excellent Alfred Russell Wallace website here. Wallace sold the property to William Hughes, founder of The Victoria Wine Company.
The Dell has survived as No. 25 College Avenue, has been a small school and for many decades as a Convent for the Sisters of La Sainte Union des Sacre-Coeurs.