In the classic fictional espionage novel and TV series Tinker, Tailor, Soldier Spy by John le Carré, the central character George Smiley, has a London flat at Number 9 Bywater Street, just off the King's Road, Chelsea, which features in several important parts of the story. The neighbouring Number 10, was actually used in the filming of the BBC TV series (source: IMDb.com).
Latitude: N51:29:25 (51.490249)
Longitude: W0:09:51 (-0.164137)
Funny thing... if you visit Bywater Street in Google Maps you can see that #8 has a Banham Security system. In Tinker, Tailor... Le Carré talks about Smiley returning home in the rain after dinner with Roddy Martindale and says "He crossed the road. His house was in darkness, the curtains were as he had left them. He climbed the six steps to the front door... There were two locks, a Banham deadlock and a Chubb Pipekey..." So I wonder if the alarm system on #8 was there around the time that the book was being written, and if so, whether Le Carré saw it... there are six step, too. :-)
NFB
@ Nigel - from the Google Street View images, it looks as if all of those houses have at least two locks on their front doors, above and below the halfway level of the door.
This is very common, to help prevent the door from easily being kicked open.
You cannot quite zoom in on those GSV images to see if they are Banham and / or Chubb locks, but if anyone does visit, please let us know and / or post a link to some digital images.