"The law doesn't say you've to own a pet," he says, with a hint of exasperation. "If you want that privilege, all we ever ask for is that you look after it. Don't batter it, make sure you feed it, if it's not well, get it vet treatment - it's not rocket science."
It isn't, but after 28 years at Scotland's leading animal welfare organisation, Flynn knows better than anyone how often human beings fail the animals in their care. "Every inspector will always give you lots of 'worst I've ever seen' until the next 'worst I've ever seen' comes along," he notes.
Often the problem is neglect, most of which is caused by the owner's ignorance about how to care for an animal, sometimes compounded by having an inappropriate lifestyle or not enough money for vet bills. He has seen cases of neglect that go "beyond belief". And then there are those deeply distressing cases of intentional cruelty. He highlights one recent case that made headlines for its barbarism. In April, a Staffordshire bull terrier was tied to a tree in Kirkcaldy before being stabbed and then doused in petrol and set on fire. The animal's killer, Alastair Graham, was later jailed for what the sheriff called the "grotesque act of savagery" and other crimes.Investigating animal cruelty and neglect is not work for the faint hearted, and Flynn spent years in a hands-on role, but these days, he spends much of his time meeting politicians and government officials to discuss how better to protect animals. However, he is also in overall charge of the SSPCA's inspectors, who investigate reports of cruelty and neglect, and ambulance drivers, who collect injured animals reported by the public, and oversees the work of the charity's 11 animal rescue and rehoming centres - a fitting role for a man who has always been "animal daft".
Flynn, 54, was born in Pilton, north Edinburgh, went to Craigroyston High School and had nine jobs by the time he was 19. Then he got a six-month job at Edinburgh Zoo at the end of one summer and stayed for seven years. After a brief interlude running his own pub in Grangemouth, he joined the Scottish Society for the Prevention of Cruelty to Animals as a relief and horse ambulance driver and has been there ever since.
Our interview takes place in an office at Balerno rescue centre, in Edinburgh, which we are sharing with three kittens, here temporarily due to a lack of space elsewhere (SSPCA centres are full to bursting with felines).
They squeak and miaow over the chief superintendent throughout. Imposing-looking though he is in his navy inspector's uniform, Flynn has an instant affinity with these tiny animals, an obvious and spontaneous affection, as he does with the dogs in the kennels out back. No wonder he works so hard to safeguard their wellbeing (he is on-call 365 days a year).
General neglect is not linked to criminality, he notes, but some forms of animal cruelty definitely are. "When you come to organised dog fighting or badger baiting, there isn't a person in my history that is a perfectly normal Joe Bloggs Monday to Friday and likes a wee dog fight at the weekend," he says. "Every single one of them is connected to various, and various degrees, of criminality. You can't even get into the dog-fighting circles unless you are introduced by somebody that is already in it and if you introduce me and I turn out to be a grass, for want of a better word, you are in big trouble. It is highly secretive.
"Scotland has still got the unenviable record of having the biggest capture of a dog fight in Europe, when 31 people were caught at a disused farm in Fife in 1991. There were people out on licence, there were people connected with organised terrorism in Ireland at the time, Hell's Angels chapter leaders, tasty tasty tasty. And a couple of them have been murdered since."
Some neglectful animal owners are repeat offenders. He mentions one man in Falkirk who has broken bans on animal ownership repeatedly and was eventually jailed. "A lot of these people, they don't stay in the housing estate, they live in the wee cottage 100 yards off the road that no one ever goes near."
Still, he believes the sanctions that exist in law to tackle bad owners, are the right ones. "I welcome the fact a lot of sheriffs are saying now that the ultimate sanction here is a ban," he says, adding that he hopes they will continue to show willingness to send people to jail if they break those bans. "The biggest prevention is that if you don't have an animal, you can't be cruel to it."
But how do he and his colleagues monitor a ban?
"The great Scottish public monitor it for us," he says. "Practically every time somebody ends up in court, it ends up in the paper. So the name's out there. Nine months later, a neighbour's on saying 'she was banned and she's got a dog'."
The organisation also relies on members of the public to be its eyes and ears when it comes to reporting instances of animal cruelty or neglect. "We don't have the manpower to go walking round housing estates trying to see if everybody's looking after their dog. So we very much react to the public and probably because our profile has never been higher, demand for our services has never been higher."
A "superb" new centre has been built in Drumoak, Aberdeenshire, bringing the SSPCA a whole new clientele, having never had a centre near Aberdeen before. Meanwhile, the Glasgow rescue and rehoming centre at Cardonald is currently undergoing a £4 million revamp to become the first two-storey kennels. This comes less than three years after the charity opened its £3.5m wildlife centre at Fishcross for injured wild animals, "an absolutely superb facility, best in Britain".
Flynn would like those who wish to take on a pet to visit reputable rescue centres first. The next best option, for dogs, is a Kennel Club recommendation of a licensed breeder, and then, for small animals, pet shops - "they're licensed, checked by the local authority, open to the public".
But the big growth has been animal sales over the internet. He warns the public to be very wary of this, especially anything that has only a mobile phone contact, since with dogs, they may result from puppy farming and animals sold this way are unlikely to have any health status or traceability. He talks about one case of a woman from Ireland who was caught with 16 pups in the car she was intending to sell all over Scotland. She advertised in local papers, offering to deliver the dogs directly to people's doors. "We first came onto that person because she brought over a litter of Dalmatians. The computer picked up reports of parvovirus in Inverness, Aberdeen, Perth, Dundee and Dumfries within the space of four days and that's really unusual. She had the same litter and had been selling them everywhere. Parvovirus is a horrible disease in dogs. It can be inoculated against in dogs when they are pups but obviously that didn't happen in this case."
If untreated, canine parvovirus is usually fatal.
When Flynn himself gets home, he does not have a pet waiting for him at present. He and his wife of 12 years, Janice, are too busy. But he has had some much loved pets, including a cat called Jade which lived to be 25, a lurcher called Libby, and, at one time, an American pit bull terrier. He had collected the dog, Lady, for rehoming and she was in his care when the Dangerous Dogs Act came into effect, leaving him with two choices - either to have her put down (as a banned breed), or to get her entered on the index of exempted dogs and pay £500 a year for her insurance. He took the latter option.
He says: "She was a fantastic dog. Because she had never been trained to be aggressive, she was an absolute gem. My cat used to batter her."
Flynn, who has a daughter, Evie, and a stepson, Ross, is now regularly visited by two neighbourhood cats who go home to their owners every evening.
The privilege of owning a pet must wait.