Kestrel in Trouble??

My girlfriend has noticed a kestrel in a local park (Mountsfield Park, Lewisham, 
London) that seems to be abnormally tolerant of humans. For two days it
has been present on low branches, feeding on insects and allowing her to
approach within just a few metres. Should we be worried that it may be
unwell?
She was able to approach close enough to take these pictures with just a
compact camera.

Many thanks for any advice,

Philip