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Update from OP. The gardener, expected at 10, turned up 40 minutes early, ignored or didn't notice the sign on the gate about dogs running free, opened the gate and three wolfhounds appeared and then disappeared down the village. It took the combined efforts of various residents, the head of the village school and a passing police patrol, and an hour, to track them down. One, a pup, was a mile away, but the two others were about two and half miles off. Fortunately, they'd come on to lanes and they could be spotted from a car,though doubtless they'd been across country in the meantime.
Ah, the joys of dogs and the countryside!