Where is the safest place to put the bird bath for my wood pigeons?

My wood pigeons love their bird bath, which was basically a large washing up bowl on a table in the middle of the patio. Since I thought it impossible for a cat or a fox to jump up without alerting them, I thought this was safe, so I was heartbroken to come back the other day and find the bowl knocked off the table and just a light scattering of feathers.

There were so few feathers I tried to convince myself he had got away, but sadly, no, his partner is now alone. I know there is a fox around and there are definitely cats, but some of the posts I have read seem to suggest that such a light scattering of feathers could suggest a sparrowhawk?

I thought putting it on a table in the middle of the patio would avoid a predator sneaking up on them, but it obviously makes them an easy target if the predator is spotting them from above. I have bird feeders on my windows, do you think placing the bird bath on a very hight trolley (over five foot) next to the wall of the house would be safer if it is indeed a sparrowhawk that has got them. I say "them" because although I have only seen feathers the once, I seem to have gone from four to one solitary wood pigeon. I feel so bad if I have made them an easy target,,,