From the Wikipedia page [1] which gives references
Channelsea Island is a small man-made island in the Channelsea River in London, near Three Mills Island in the London Borough of Newham.
It was created in the 11th century to house the Abbey Mill.
The island was purchased in 1996 by the Abbey Mills Riverine Centre Trustees, a Muslim organisation seeking to develop a mixed-use development centered around a large Mosque, as part of a 16.5 acre land parcel made up mostly of the site to the southeast of the island.
The Abbey Mills Riverine Centre Trustees put in a Planning Application for all of the land, except the Channelsea Island, in 2012, and this planning application was refused permission by Newham Council. The island has been described as "a haven for wildlife and untouched for many years".
The Remote London page is [2]