Not seen today at all, so I'm a fraud.
But on Saturday, in Stratford, I was distracted by something falling on the ground from an arch beside a building.
I thought it might have been pigeon droppings, but there was a lot of it coming down, so I looked closer. It wasn't from under the roof bit, but from behind. I then saw it was moss.
OK, I thought, someone's cleaning the rooftiles the other side. No ladder apparent, so I thought I'd have a look.
It wasn't a person; it was a thrush-sized bird (couldn't see clearly as it was silhouetted and flew off fairly sharpish). It was hopping along the roof picking up the blobs of moss and, rather than flying off with them for nestbuilding as I would have expected, dropping them over the edge of the gutter.
It's possible the bird was planning to come back later & pick them up off the ground, but there was more than might be needed for a nest.
I wonder if there was something in the moss that the bird was eating, or collecting for its young...