White works well with the yellow, white and red of the room, and white grout makes the metro tiles read more as a textured surface than as a brick pattern. They don't try to be the main feature. There is already enough going on in the room.

And then somebody puts an aluminium trim on top.

It is stylistically foreign to the room. Against the cornice, parquet, traditional furniture – and the tiles themselves – the profile looks exactly what it is: a tiling accessory. It makes an otherwise restrained surface look cheaper and clumsier than it needs to.

Metal or plastic trim is particularly difficult with metro tiles, although not inherently wrong.

Metro tiles already have an edge language of their own. Traditional ranges often included rounded or glazed finishing pieces: bullnose tiles, cappings, external corners and other specials. Even when modern metro tiles don't offer these pieces, their bevelled, ceramic character still suggests that kind of termination.

An aluminium profile introduces something quite different: a thin, mechanically precise strip of metal. With large-format contemporary porcelain that can make perfect sense. The profile belongs to the same precise, engineered vocabulary. With traditional-looking metro tiles, it can look as though a modern fixing solution has been placed on top of an older design language.

Plastic is usually worse. White plastic beside white ceramic rarely disappears as successfully as one might expect. Differences in gloss, colour and ageing give it away.

None of this means no trim with metro tiles. Black or brass metal, for example, can be deliberately incorporated into a contemporary scheme where metal is already part of the design. Stainless steel can belong in a genuinely utilitarian or industrial interior. The difference is that the trim has been designed in rather than used to finish the job.

For a traditional interior, I would rather see a ceramic finishing piece where the range provides one, a carefully detailed exposed glazed edge, a termination into another architectural element or, if necessary, an extremely discreet profile.

Borders have always mattered in tilework. The Romans didn't put them around their mosaics for nothing. An edge doesn't merely finish a surface. It helps tell us what that surface is.

This is what bothers me at Press Coffee. The metro tiles are simple and familiar, which is precisely why they work. But the aluminium trim exposes the system by which they were installed. You stop seeing a tiled wall and start seeing tiles + grout + trim.