You know, I see this type of thing quite a bit... more than you'd think. For a big city that can seem impersonal and soul-less at times, it is the odd little things that bring a smile to my face and remind me of the small day to day considerations of others.
Now, think back....how many times have you been walking down the street and remark to yourself "Oh dear, someone has dropped a glove"... "Oops, someone has lost a shoe"..."dropped an umbrella"..."lost a jacket". In the US, we would normally just walk on by (sad commentary, I suppose).
Not in the UK...people will pick up the lost item and drape it over a fence, tack it on to a tree, lay it gently against a wall. It is as if people want to say to the person who list the item, " I found your personal belonging and have left it here for your pick-up". Point in case:
In the hustle and bustle of today's world, it is touching someone took the time to pick the item up and display it along the manic streets of London in the hopes that its owner would come looking for it.