Sir – C.P. Snow, where are you in this hour of need? I can understand Christopher Gray’s annoyance at poop-splattered windows (Gray Matter, January 22), but his bafflement is easily remedied.

The emissions of flying gulls have lateral momentum (upon release travelling at the same speed as the bird), and so do not descend vertically. A cunning bird can release a payload then wheel gracefully away from Mr Gray’s windows.

The well-aimed poop descends on a curved trajectory, with messy results. Whatever can these birds have against the occupant?

David Colbourne, Witney