Crane and ?

London Bridge. I am meeting some of my Women in Property friends this evening for dinner at Jamie's on Tooley Street. I was hesitating to go what with the report for the CIOB (just about done) and Mum (didn't visit her today) but am very glad that I did. We shared lots of stories of woe and had a good laugh and lots of mutual support. 

I have a few photos of the Shard but have blipped that many times. So this is a crane that is just to the right of the Shard (from where I was standing on Tooley Street). But what is the yellow, back to front S thing that has photobombed the picture?