Thank you Darek for the following (amazing) observation and photos;
Walking past Shed #4 on Oct 14th, Darek was surprised by a number of squawking crows chasing a hawk around the tree behind the shed.
The perched hawk was repeatedly swooped and circled by crows, generally leading to an exit then return to the tree.
Later in the afternoon, another gardener witnessed a raptor swoop down and snatch up a rat near the Experimental Plots - this may have been the same bird!
Darek has (tentatively) identified the raptor as a pigeon hawk (merlin) based on its size, colour and tail banding.
This observation of the pigeon hawk catching the rat shows the value for gardeners of making the Community Garden "bird friendly". Small birds eat caterpillars, aphids and beetles; and the larger birds eat mice, voles, rats and rabbits.
