If it weren’t for hoverflies, this letter might well have proven rather tricky. Fortunately, there are three genera of hoverfly in Britain with names beginning with X: Xanthandrus, Xanthogramma and Xylota. I have seen none of the first but I have seen one of the Xanthogramma species, X. pedissequum (there are two others that have so far eluded me, X. stackelbergi and X. citrofasciatum).
There are seven British species of Xylota, of which I have so far encountered only two, X. segnis (below left) and X. sylvarum (below right). I’m still finding hoverflies a rather tricky family to identify but these particular finds have been confirmed through a series of photos by those much more expert than I will ever be.