You know that there is something afoot when walking into the entrance hall of a flat for sale in a Chelsea street and noting there are no doors leading off the entrance hall. Then it dawns on you that the reason why there are no doors leading off the hall is that the entrance hall is the flat.

This property, which is going on sale this morning (and, given the currently frenzied state of the London property market, may already be firmly under offer), measures 12ft by 6ft. It is on the market for £170,000 and it requires a further £30,000 to be spent on it before anyone could move in.

The flat is thus the size of a championship snooker table. In both cases, deep pockets are a useful accessory. To conceive of an area this size as being worth £170,000 stretches the boundaries of both arithmetic and the imagination. To call it a flat stretches the boundaries of language.

It is hard to imagine how estate agents could seduce potential buyers to such a property, even given their legendary taste for investing words with meanings that would make Samuel Johnson queasy (“stunning rooftop views” — the flat is up seven flights of stairs; “fashionable decor” — it was fashionable in 1972; “lends itself to reconfiguration by an imaginative buyer” — the bedrooms are situated in the garden shed; “a fragrant home” — it’s located above a takeaway).

And that is before the extra £30,000 enters the equation. Given its size, this suggests the purchaser plans either to gold-plate the walls, or will be getting it repainted by a moonlighting Premiership footballer charging his usual hourly rate.

Maybe the sale particulars will settle on: “Must be seen to be appreciated”. It’s a phrase agents sometimes use for “must be seen to be believed!”