An Exercise in Frustration

Ever had one of those days when you spotted something interesting, but it wouldn't sit still, and certainly wasn't going to come out of focus-wrecking cover?

Reading, UK, and I think this is a female Blackcap (which of course doesn't have a black cap, only the male does). The final shot is from significantly later in the walk, so is probably not the same bird - but gives you a sense of what I wanted (still not sharp enough though!).