The Metropolitan Drinking Fountain and Cattle Trough Association was set up in London by Samuel Gurney, an MP and philanthropist, and Edward Thomas Wakefield, a barrister, in 1859 to provide free drinking water. Originally called the Metropolitan Free Drinking Fountain Association it changed its name to include cattle troughs in 1867, to also support animal welfare. It must have been difficult to get such a long name onto their drinking troughs. The trough below must have been for dogs.
In this photograph, Barnes Pond is in the background. The area around Barnes Pond is carefully brightened with wildflower areas and other plantings as seen here. Another example of a former horse trough can be seen at https://www.geograph.org.uk/photo/2586889