Why do Ravens hang around in cemeteries? If you read the answers posted across the net you will find that the crow family (which contains Ravens as the large scruffy cousins) are thought to be the escorts of souls to the afterlife.
Realistically, Crows and Ravens are carrion eaters, and are attracted by the smell of death.
They are beautiful birds, and apparently highly intelligent, for birds anyway. Finding one perched on a gravestone was an open invitation.
Photocollages can be fun. This is comprised of at least six separate photographs, taken at various times in various places. The old lady is a regular outside Shepherds Bush Tube Station where she plays lively tunes on a recorder. The tree was growing from the mud of the Thames on the Hammersmith towpath, and the tomb itself is in Kensal Rise cemetery.