This is the corner of Waterloo Road and Alaska Street. I'm not sure how long this sign has been there, but I'd like to check out the area around the bottom right of the sign. In the crack and behind the back, if you know what I mean.
Let's try one more at the St. James C of E Church in Clerkenwell. This one is on the west side of the church, to the right of the stairs leading up to the door. There is an arch there with a metal grate in the center of the wall under the arch. Inside the grate.