The Gilbert and George exhibition currently at the Tate Modern (until 7 May 2007) is the first retrospective covering their career from the very beginning up till now. The exhibition fills an entire floor, including the concourse between two galleries and the espresso bar. That's a lot of Gilbert and George, also because the works they have created since the 80s are typical museum or corporate art that doesn't fit into an average living room. I must say that by the time I reached the espresso bar, half way through the exhibition I felt like having an espresso, which says something since I don't drink coffee.

One of the interesting aspects of retrospectives such as this is that you can see the first tentative, sometimes directionless, steps before an artist hit upon his theme, works that are often buried inside museum depots and private collections. You also get to see the dead ends when a theme turns into mannerism and the explosion of creativity when a new theme is found.

The work for which Gilbert and George are known has a very distinctive signature and over the past 40 years they have explored every corner of their self-defined aesthetic universe, consisting of photo montages laid out in a rectangular grid.

I find their work most interesting when they engage with the city, as in their "Dirty Words Pictures" (1977), one of my favourite works of art. It was a delight to see almost the entire series together in one room. These works have a very raw energy and still seem relevant and urgent. They document urban life and are also reflective of art and the artist. Their self-centered works from the 80s and 90s leave me largely indifferent though. They are too big and not very subtle. Strangely these pieces work much better as reproductions.

Gilbert and George are an institution. For more than 40 years they have performed as Gilbert and George. They act in unison and speak in one voice. They dress identically and play the part of the English gentleman to perfection. There is something odd about this, because Gilbert Proesch is actually Italian. In order to become the Gilbert in Gilbert and George he had to give up his own identity. I wonder whether he spoke Italian when they were in Venice for the Biennale in 2005.

As I walked across Blackfriars Bridge towards Blackfriars tube station I also wondered what would happen if one of them died. Would the other continue being either Gilbert or George?

Gilbert and George: Major Exhibition is at Tate Modern, London until 7 May 2007.