You can hear Bert before he enters the waiting room. As the ferocious snarling starts, far outside in the car park, the demeanour of the clients sitting nearest the door changes in distinct waves.

First, an alarmed look on their faces. They exchange nervous glances, nodding in agreement; already a protective unit. Cat baskets are swept up from the floor and sat defensively on knees; only toes touching the floor for maximum ground clearance.

Similarly, small dogs are lifted to the relative safety of their owners’ arms. Furtively, the group slides, as one, further along the seats, putting as much distance between themselves and the anticipated arrival of what must surely be 50kg of aggressive canine.

As the door swings ominously, their mouths fall open and they gasp as the diminutive Jack Russell enters the area. Alert and menacing, Bert scans the room, apparently searching for his next prey; despite his small stature, humans and animals try to avoid his direct gaze, lest they incur his wrath.

But, inevitably, another patient makes accidental eye contact with him and the noise begins again. Bert growls and barks, teeth flashing, while his wee legs seemingly scramble to get away from his owner, who grips him tightly and purrs that he is a ‘naughty boy’.

His behaviour continues to the reception desk, where, as always, the staff confirm that he is booked in and suggest he might be less stressed if he were to wait outside in the car until the vet is ready to see him. There is a collective and audible sigh of relief as he departs, but few people know the whole story.

Bert is not a bad dog. He is not even an aggressive dog. He is a scared dog. Actually, a petrified dog. Big dogs totally freak him out. Little dogs make him very uncomfortable. Middle sized dogs put the fear of death in him. And his hysterical response to exposure to them is predictable and rational.

His problem is two-fold. Identified by his owner as a frightened pup, she scooped him into her arms protectively whenever another dog appeared, no matter how pleasant they were.

Some early socialisation with friendly, playful, well-adjusted companions at this time in his life would have done him some good. But it was not to be. Meeting other dogs was made into a stress-filled situation.

Later, as he matured into a young adult, he began to believe that his growling and snarling at passing dogs was what kept them away. So he continued to do it more and more; the behaviour became self-perpetuating.

Now viewed by many as an aggressive dog, his owner was persuaded by friends, neighbours, fellow dog walkers and Google that castration was the answer. He was booked into a vet practice, who asked no questions but did the deed well enough. And things just got worse.

A reduction in his testosterone level further exacerbated his underlying lack of confidence and, by the time Bert was presented to us for discussion about his behaviour, the situation was almost out of hand.

Poor Bert; a most misunderstood wee dog.