The famous monument which gives its name to an underground station and the adjacent area was never meant to be where it is now. Originally designed in 1827 as a grand entrance for Buckingham Palace, it was moved here in 1851.
Lots about it on Link
The Millennium Edition of Brewer's 'Dictionaryof Phrase and Fable' mentions that the site of Tyburn Tree (gallows) is 'marked by three brass triangles let into the pavement at the corner of Edgeware Road and Bayswater road'. Executions ended there in 1783. May we have a photo please from one of you Marble Arch GEOGRAPH-ers?