Whenever my children ask if they can have a dog, I always take a firm line. We don't have room for a dog, I tell them. And even if we did have room, we don't need the added responsibility. Rearing three small humans is complicated enough without having a pet to worry about as well.
But in what must have been an unguarded moment earlier this summer, I allowed my seven-year-old son to attend an audition at his music school, unleashing a chain of events that ended recently with my purchase for him of a cute, miniature cello. And only now are the full implications of this purchase dawning on me.
A cello is not just for Christmas, or even for Halloween. Ours is still only a pup - a "one-eighth" they called it in the shop. But it's already the size of an adult Labrador, and that's only the start of it. If the classes continue indefinitely, we will end up with a St Bernard.
In fact this was the instrument's whole attraction for my son - that it dwarfs his older sister's violin. Which brings me to another issue in the pet-versus-cello debate. On the plus side, you don't have to clean up after a stringed instrument. You do, however, have the noise problem. It can take years for even one of them to be fully house-trained. In the meantime we face endless nights of listening to the violin howling in one room and setting the cello off in the next.
The cello's domestic arrangements are demanding enough. But already I worry about the longer-term future. What if my son turns out to be a musical genius - every parent's nightmare - and has to start travelling the world to play? The British virtuoso Stephen Isserlis spoke in an interview lately of how he always has to buy an extra seat on the plane for his cello, which is too valuable to put in the hold. The expense is such that, as retaliation for the refusal of most airlines to give the instrument frequent-flier miles, Isserlis makes a point of ordering it a (kosher) meal on long-haul flights.
Cost is not the whole story, either. The freedom to bring his cello on board was retained last year only after a threatened march on the Houses of Parliament in protest at the new anti-terrorism rules on cabin luggage. And even when a cello has its own boarding pass, the cellist is still at the mercy of airport security.
Julian Lloyd Webber had a gun pointed at him once when, despite having a ticket in the name of "Miss Cello" (airline computers insist on all passengers having a personality), he had to defy a guard who demanded he consign the instrument to cargo. Elsewhere, his cello's adjustable metal leg has been confiscated as a weapon, and he lives in fear of the day that security staff decide the D-string could be used to garrotte a pilot.
Lloyd Webber too has attempted to claim air miles for his instrument, but jokes that the ruse is always defeated when he gets to the part of the registration form asking for the passenger's place and date of birth. "Italy" and "1690" - it's a Stradivarius - tend to give the game away.
There would be no such worries - for now, anyway - with my son's cello. It was born earlier this year in China, so the biggest risk would be that the air-miles people might report us for illegal adoption. But it will be a while yet before the international invitations start arriving, anyway.
Until recently, I might have said that the cello was not one of the "sexier" musical instruments. That was before I saw the rising English star Natalie Clein playing it on television. With her gender, beauty and expressive style, Clein is seen by some as the Jacqueline du Pré of a new generation. And I have seen the instrument in a whole new light since watching her in action, her hair damp with perspiration and cascading down her face in dark ringlets as she writhed in passionate embrace with Elgar's Cello Concerto. I needed a cigarette afterwards.
At the other end of the spectrum was Mstislav Rostropovich, the great cellist who died earlier this year aged 80. Born in Azerbaijan, he had been a fearless opponent of Communism in the Soviet Union, doing with music what Alexander Solzhenitzyn did with words. When the Berlin Wall fell, according to one obituary, he celebrated by playing Bach suites all night "in a breach between the concrete blocks".
So the cello is both an exciting and a noble instrument, and I suppose it's fun to be starting out on a journey with it that might last a lifetime.
Even so, I'm troubled by the words of Julian Lloyd Webber who, reflecting on the many shorter journeys he has made along the way, blamed his mother for not nipping the whole thing in the bud. "When I was four and I asked her if I could play the cello," he quipped, "she should have mentioned the many attributes of the piccolo."