Duplicate numbering of houses

The number 12 appears on the gate leading to the basement of No 17 Nevern Road. The house numbered 12 is on the opposite side of Nevern Road with the other evenly numbered houses (SW5 9PH). Can one property have two different street numbers? The landlord has been informed.

Nothing done yet. Considering the property is supposed to be situated in a conservation area I would have thought correct numbering would have some relevance.

Nothing done about double numbering on door, although the landlord suggests the second set of numbers relates to Flat 17 at 17 Nevern Road. (The postal address I understand for 11-17 Nevern Road is "15 Nevern Road".) The landlord admits that the second set of numbers are probably unnecessary, but they still remain on the door. The number 12 still appears on the gate to the basement, which presumably relates to Flat 12, 17 Nevern Road, only it has now been upgraded from plain figures '12' to ornately decorated tiles portraying the No 12, which has done nothing but worsen the appearance of the building. The number 12 also appears on the wall going down the steps to the basement, with a large ornate cameo-style plaque also affixed to this wall. It would be more in keeping with this conservation area if No 17 Nevern Road (basement and ground levels, front of house) could be brought more into line with all other properties in the road.