Back home, with so little dog experience, I was flummoxed by Reggie. He had so many alien habits: why did he stalk me around the house – abandonment issues, maybe? And the incongruous growls at 4pm each day? (He's so quiet and unaggressive otherwise, I first thought he might be mute.) Reggie also loves everyone. With sometimes startling abandon: he's like the stereotypical Italian mama towards visitors; strangers' laps are a home-from-home and at the pub he rolled wantonly on his back, glancing between punters to gauge the attention he was garnering. A need for approval, rooted in his puppyhood neglect, perhaps?

So when the opportunity came for a consultation with Dr Roger Mugford, the country's top animal psychologist, to solve some of these puzzles, I was in. Naturally, I had some misgivings: broadly in the shape of Paris Hilton's chihuahuas (they live in their own tiny house) and Rosie from Made in Chelsea (whose dachshund, Noodle, was diagnosed as "lonely" by her dog shrink). Along with canine clothes, dog aromatherapy and pooch-friendly sushi, therapy for the four-legged does sound like something for those with too much cash and not enough life skills.

"Ha ha, yes I agree," says a reassuringly down-to-earth Dr Mugford when he arrives for our session. "I'm not like a New Yorker analyst that deals with the super-ego ruining your dog's life. That's all nonsense." Reggie is not a typical Mugford case: this morning, for example, the doctor has been in court helping to defend a staffie whose teenage owner "cares very well for the dog but sadly has a long criminal record".

"When your dog is threatening your marriage or attacking people – that's when owners need me," he says. Which arguably justifies the £200 he charges for a consultation. "I know I make massive differences and usually very quickly."

Mugford pioneered the science of pet behaviour in the late 1970s and has a zoology and psychology BSc and client list including the Queen to back him up. Her Majesty called on him to troubleshoot pack problems in her corgis. "She's astonishingly good with animals," he says, "so it wasn't a sign of weakness."

But he thinks his most successful case was Kevin, a homeless guy, whose dog's life was on the line after it attacked police officers. Kevin frequently passed out from drink or drugs, and the police had come over to help him. But Kevin's protective dog didn't see it that way. Mugford's winning preventative measure was a double-ended lead to attach the dog to his master. Constrained, it was far less of a public risk. "Dog behaviour is very simple," says Mugford.

Nevertheless, canine psychology is an increasingly popular service. Deborah Bragg, who runs The Canine Behaviour Centre, which sells training packs to aspiring dog psychologists, says that, year on year, demand has steadily been increasing by 15-20 per cent. She believes it's the stressful lives we now lead – and which we, then, subject our pets to – that are driving popularity. "If you're out eight hours a day, six days a week – you're going to get behavioural problems," Bragg says.

Sarah Wright, editor of Your Dog, agrees. "Dogs don't lead as natural a life as a pet as they once did." She's not against the idea of dog psychologists: "Yes, there is an element of going OTT with some – but people wanting to understand how to live and interact better with their dogs is good." For those who book a session with Dr Mugford, you get at least two hours, where he asks questions and observes the human-animal interaction indoors and on a walk. So what can he tell me about Reggie?

"He's incredibly sensitive," Mugford says, noting a little "stress yawn", often misinterpreted as tiredness. "It's in fact a signal he's unsettled because we're talking so he's not getting any attention. Dogs that yawn a lot tend to be very sensitive." Unsurprisingly, Mugford quickly deduces that Reggie is "a promiscuous little fellow", and a "sensually skillful canine tart". Not only is he gushing over Dr Mugford, but he's wooed the cat-loving photographer, Teri, too.

My ego is saved when Mugford recognises that Reggie is primarily devoted to me. Hence the stalking: "It is a predatory trait that's evolved into play, and you are his only social outlet. In an ideal world, you'd get another dog to divert his social curiosities. People with two or more dogs tend not to have these complaints." Failing that, Mugford concludes, I should "take it as a compliment".

What about the weird barking? "So many people misunderstand vocalisations. Dogs are vocal. It isn't a threat. It's attention-soliciting. And it works. So he does it again." Hmm. Yes, and just when he wants his pre-dinner walkies. "Dogs are great receivers of human information and learn to manipulate because they get pay-offs."

This is all very interesting, but it's time to come clean about one of Reggie's less funny little ways. I'm almost ashamed to admit that Reggie is coprophagic. It means he eats what other dogs expel. He also likes to roll in it. Both deeply antisocial habits. The vet's already ruled out malnutrition (a common cause) and said: "Unlucky, he just likes it." How could a psychologist help?

He may have been deprived of food when he was a puppy, concedes Dr Mugford, prescribing Pet Corrector – a small canister of compressed air that emits an off-putting hiss that a less sensitive dog might ignore. We test it on a walk: Reggie makes a beeline for something revolting. Mugford activates the spray: bingo, Reggie is startled away. "It's an aversive approach," Mugford explains. "You can't reward a dog for not doing something... And I have been criticised by some of these trainers, what we call the 'Treat Taliban', who believe that everything in life can be achieved by rewarding good behaviour. What I seek is a balance between the two."

Mugford is the opposite of the treat-dogs-like-they're-wolves brigade, and gets cross about "people on television telling you to apply general rules to all dogs. No dog is the same!"

On that note, Reggie and I bid him farewell. "It's been an honour," says Dr Mugford. "Despite the shit thing. With all his qualities he'd have great genetic potential to sire lots more little Reggies." Aw, I feel proud. If only he hadn't been neutered.

Dr Roger Mugford consulted Reggie courtesy of the film 'Beginners' which is out on Blu-ray and DVD from Universal now