The Hextol German Shepherd Lexy is getting a little old and doddery now. She is nine, which makes her a positive pensioner in canine terms, and the elastic has gone in the bounding gait which once saw her clear a five bar gate with ease.

She hirples along gamely, but gets seriously out of puff if I take her too far on her daily constitutional.

She likes nothing better than when the grandchildren come calling. She tries to climb on their laps, as though she is still a puppy, despite the fact that she is bigger and heavier than all of them.

She will play ball with them for hours and tolerates all manner of indignities at their hands and at their paws of their cockerpoo Darcie. She looks on coolly as the youngster helps herself from her dish, and it is only under supreme provocation that she will occasionally swat the junior dog into place with a massive paw.

She is perhaps the hairiest dog on the planet, and is in a continual state of moult, releasing enough hairs every day to fill a mattress. No matter how long and how hard you brush her, she leaves enough hairs on your trousers to stuff three cushions as she slinks past on her way back to her basket.

Her once black face is now a whiter shade of pale as the grey hairs come through more abundantly every day, and she looks every inch the canine codger.

But should anyone have the temerity to come to the door of Hextol Towers she throws off the years like a cloak and goes into full attack mode. She literally bristles with indignation, blowing herself up to twice her already impressive normal size, and barks like the Hound of the Baskervilles on steroids.

Because of her super protective attitude, we have had to set up a network of security measures to protect any legitimate callers to Hextol Towers.

There are Beware of the Dog notices at front and rear entrances, a large bolted gate between front and rear gardens and the rear gate has a security chain to prevent people walking in unannounced.

Any non-family visitor who tries to reach through to unlatch the chain risks losing several fingers, if not the whole hand.

Inside, we have baby gates on every door to prevent her gaining access to callers, although if she really puts her mind to it, she can jump the gates anyway from a standing start, flowing over them like lava from a hairy volcano.

On one occasion she did bypass the security network, as some foolish fellow had left the garden gate open just as an earnest young man was calling to deliver pamphlets of some nature.

He showed a remarkable turn of speed to beat the dog by milliseconds, hurdling the hedge into next door’s garden as Lexy lacerated his briefcase.

She was asleep the other day when we had a visitation from a young double glazing salesman, but his gentle tap on the door turned her from slumbering doormat to a slavering Cerberus in the twinkle of an eye.

We put her in the back garden before letting in the young man, whose confident smile slipped a little as he heard the gale of noise coming from outside.

Part of his visit involved measuring the conservatory windows, a process which brought him face to face with the dog, separated only by two thin panes of double glazing. “Her tail is wagging,” he quavered. “Does that mean she is starting to like me? Perhaps if I went out and gave her a biscuit she might calm down.”

“If you gave her a biscuit, that would only be the starter – you would be the main course,” I replied with relish.

I took pity on him, and said that if he sat down, I would let the dog in, and I could almost guarantee she would not touch him, but he wasn’t prepared to take the risk for some reason.

He was with us for about half an hour, which is a remarkably quick visit for a double glazing salesman, and she barked ferociously throughout.

“Is it even legal for anyone to have a dog as fierce as that?” he asked as he prepared to leave, and I assured him she was as docile as a kitten when she wasn’t defending her home.

I gave the dog a biscuit before his car had left the estate.