Tavistock Terrace is a quiet, fashionable street in Upper Holloway. Most of the houses are three-storey, with a "downstairs" for the cook or maid, and date from about 1860. It’s all very quiet and conventional – the epitome of Victorian respectability.

The street would have been well established by the time Charles and Carrie Pooter and their wayward son Lupin – the family at the heart of the late-Victorian comic classic, the Grossmith brothers’ The Diary of a Nobody – moved in nearby. The Pooters proudly gave their address as The Laurels, Brickfield Terrace, Holloway.

Mr Pooter described his new home as "a nice six-roomed residence, not counting basement, with a front breakfast-parlour".

"We have a little front garden; and there is a flight of ten steps up to the front door...We have a nice little back garden which runs down to the railway. We were rather afraid of the noise of the trains at first, but the landlord said we should not notice them after a bit, and took £2 off the rent."

The desirable residences of Tavistock Terrace have something which the Pooters’ home lacked: gnomes. They’re still there – dozens of gnome-like decorative heads above front doors and ground floor windows. At a rough count, the Terrace still has 64 of these heads on 33 houses. That’s almost as many gnomes as residents.

"The gnomic figures are a source of constant discussion and we often see people looking up and pointing as they walk past," one long-standing resident of the street tells me.

"For a long time we assumed they were an image of the architect or builder but I’m afraid it’s probably more mundane than that."

It’s unlikely that either architect or builder immortalised themselves in this manner. But it’s far from clear why this terrace, alone of Upper Holloway’s Victorian streets, is a sanctuary for these cheerful looking faces.

"We think the builder had a mould made of these faces," another resident confides. It’s quite possible that a developer, anxious to make his houses stand out in a crowded property market, either devised a design and had these ornamental faces made to order or perhaps picked up a job lot from a builders’ yard.

Many Victorian terraces sported distinctive ornamental plaster and stonework and sometimes these featured stylised faces. These were often based on classical or mythical figures; capped and bearded gnome-like features were not so common. And a conclave of gnomes is distinctly unusual.

The gnome, or goblin, was a mythological figure which came into vogue in nineteenth century fairy tales, sometimes being seen as a household sprite which brought protection and good fortune. That could be why they decorate Tavistock Terrace.

In other corners of London, there are some similar architectural features. On Manchester Street in Marylebone, several houses - rather grander and older than those in Upper Holloway – also sport some gnome-like faces. But these have a fuller beard and are nothing like as convivial as the gnomes of N19.

"They’re charming," says one woman whose Tavistock Terrace home sports two of these heads. "It’s especially nice that on the north side of the street they are almost complete."

Not all the houses have these heads, but the preponderance suggests very strongly that almost all the street was built by a single developer. Much Victorian house construction was speculative, with small builders constructing just a handful of houses. That’s why so many Victorian streets have minor variations in architectural detail: the ornamentation; the style of the windows; and the porches and door surrounds. Tavistock Terrace is unusual in its uniformity.

And the gnomes should have a secure future. Not only are they keenly appreciated by the householders of Tavistock Terrace, they are also in a conservation area.

Andrew Whitehead is a historian and the author of the Curious series of books about localities in North London.