"I can't believe I'm related to that . . . that . . ." expostulates Ethel about her brother, having discovered a frog in her hatbox. "All families, " says Mr Brown sonorously, "have their dark side, Ethel, and I'm afraid ours is darker than most".
Mr Brown is a man of laconic humour and a gentle philosophical bent. But then he has to be. He has been known to generations since the early Twenties as one of this country's most famous fathers, since he is the sire of none other than William Brown, otherwise known as Just William (Sundays, 5.35pm, BBC1, November 13).
"Time in William's unnamed village has almost stood still and the golden glow that hung over it through the Twenties, Thirties and Forties has lost none of its lustre," wrote Mary Cadogan in her 1986 biography of William's actual creator, Richmal Crompton The Woman Behind William.
Much the same can be said of this 1994 version, independently produced for the BBC by Talisman films. Colours glow sharper than summers of yesteryear, flowers bloom taller, fires burn brighter. The affluence of rural England is the backcloth, households have servants, mothers are swathed in furs and hats fit for the Queen Mother.
These are tales in which mischief is mischief, rooted in prankishness and innocence, when the term "yob" (boy spelled backwards) had not been invented. That's not to say that miscreants, rascals and rapscallions got off scot-free. They didn't.
In Sunday's opening episode "William and the White Elephants", as William and his cronies strive to make the best of a bad situation of their own making, William knocks at a grand front door "Clear off, you cheeky monkey," says the indignant maidservant. Then thwack! She smacks him hard on the face.
As William nurses his war wound and prides himself on it as a trophy, his friend tries his luck. "We're not at home to Mr Rude!" snorts the maid a dead ringer for Mrs Danvers and thwack. Another clip round the ear.
One of William's great strengths is that he is a boy of any era. The stories were first written by Richmal Crompton for adults in 1919 when she had to abandon teaching because of polio. But the books (first published in 1922) became children's classics to generation after generation, including this one.
This winter plum serial is very much a period piece which curiously separates its William from the 10-year-olds of today and may appeal more to their teachers and parents.
That David Giles, the director, also made The Darling Buds of May comes as no surprise. There are strong similarities between the two productions: echoes of the Larkin family linger in the Brown household. The music, self-consciously impish, is intrusive and detracts at times from the dialogue.
This Just William has been played for comedy value, sometimes to the point of farce. It could have had subtler touches in performance and direction but the writing is always strong.
A whole generation of child actors has been schooled in the performances of the hard realities of modern life in long-running series like Grange Hill and Byker Grove. Perhaps for that very reason, the younger children in this production have a harder road to hoe. It's one thing to be cute, another to be twee. For their ages, they cope manfully.
Oliver Rokison plays William, while David Horovitch and Polly Adams, as William's parents, convince you that they have lived through it all. Theirs are the best performances.