From this site Guglielmo Marconi made the first public transmission of wireless signals on 27 July 1896

Photo of Guglielmo Marconi grey plaque
kokeshi on Flickr
Photo of Guglielmo Marconi grey plaque
Man vyi on Wikimedia Commons PD
Photo of Guglielmo Marconi grey plaque
Spudgun67 on Wikimedia Commons
Photo of Guglielmo Marconi grey plaque
Julian Osley on Geograph
Photo of Guglielmo Marconi grey plaque
Matt Brown on Flickr
Photo of Guglielmo Marconi grey plaque
Spudgun67 on Wikimedia Commons
Photo of Guglielmo Marconi grey plaque
Peter Olding on Flickr

Newgate Street, London
Google Streetview

Colour: grey

Wikimedia:

Flickr:

See also...
Photo of Guglielmo Marconi blue plaque
Spudgun67 on Flickr
Photo of Guglielmo Marconi blue plaque
Peter Reed on Flickr
Photo of Guglielmo Marconi blue plaque
rw_norris2000 on Flickr
Photo of Guglielmo Marconi and Nellie Melba blue plaque
cazphoto.co.uk on Flickr
Photo of Guglielmo Marconi brass plaque
Paul Mison on Flickr
Photo of Guglielmo Marconi and Wireless Telegraph Company Limited blue plaque
Stuart Axe on Flickr
Photo of Guglielmo Marconi and George Kemp blue plaque
Kay Atherton on Geograph
Photo of Madeira Hotel, Court Royal, and Guglielmo Marconi blue plaque
Elliott Brown on Flickr
Photo of Wireless Telegraph Company Limited, Nellie Melba, and Guglielmo Marconi bronze plaque
Nick Harrison on Flickr
Photo of Guglielmo Marconi gold plaque
Simply Jan on Flickr
Photo of Guglielmo Marconi gold plaque
Simply Jan on Flickr
Photo of Guglielmo Marconi marble plaque
Eugene O'Loughlin on Flickr PD 1.0