In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Bishopsgate like this:
BISHOPSGATE, a hamlet on the N border of Surrey; adjacent to the Great Park of Windsor, near Virginia water. It lies amid charming scenery; and was the place where the poet Shelley wrote his "Alaster."
Additional information about this locality is available for Egham
GB Historical GIS / University of Portsmouth, History of Bishopsgate, in Runnymede and Surrey | Map and description, A Vision of Britain through Time.
Date accessed: 30th April 2017
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