Robert Ballagh's exhibition, Towards a Portrait of Louis le Brocquy, will be presented at the Gorry Gallery, in association with Damien Matthews Fine Art, from 28 June to 11 July. It features some 22 sketches, drawings, photographs, watercolours and oil paintings of le Brocquy, all of which are studies towards the final, large-scale portrait, which will also be on display. It took Ballagh an entire year to complete the painting, and the exhibition should give an interesting insight into the artistic process of creating a portrait from start to finish.

It should also be revealing about the relationship between the two men, who have been friends for some 40 years. Le Brocquy, who is 27 years Ballagh's senior, was an early influence on the younger artist. Indeed, one of Ballagh's first works, 'The Blessing', which was painted at the age of 16, was inspired by le Brocquy.

According to Damien Matthews, the commission for the portrait came about early last year. He and a client (who prefers to remain anonymous) were discussing Ballagh's portrait of the author JP Donleavy, painted to celebrate his 80th birthday, when the client wondered if anyone was painting le Brocquy on the occasion of the artist's 90th birthday.

Apparently, there wasn't. So between them they decided that Ballagh "was the man to do it"; the client agreed to sponsor the portrait, and Matthews approached Ballagh the very next day.

Le Brocquy, not keen to spend hours of his precious time sitting for a portrait when he could be doing his own painting, was hesitant about the idea at first, says Matthews. However, he relented once he realised that Ballagh would take photographs and quick sketches and use them as source material for the piece, rather than have le Brocquy endure seemingly endless sittings.

The end result is a large oil painting of le Brocquy, elderly but dignified, working at his easel.

The canvas on which le Brocquy is working extends beyond the two-dimensional picture plane, while his palette is also three-dimensional, with a real brush protruding from it.

In a nod to Velasquez, we can only see the back of le Brocquy's canvas, and a self-portrait of Ballagh taking a photograph is hanging on the wall behind him . . . a gesture of homage, but also of authorship.

This is le Brocquy through Ballagh's distinctive lens.

All works in the exhibition will be for sale, with prices starting at 5,000 and reaching a whopping 265,000 for the finished portrait. If that's out of your price range, you could always pick up one of 100 limited edition prints of the portrait, each of which are signed and numbered by Ballagh, for a more reasonable 2,650.

"Everything is for sale . . . including the large oil portrait, " says Matthews, adding: "But, if possible, Ballagh and I would preferably like it to go to a public collection . . . where it belongs."

There seems to be something slightly self-serving and (dare I say it? ) self-important about such a desire. But then, I'm sure many would agree that there should be a portrait of le Brocquy in a public collection. Any takers?

Towards a Portrait of Louis le Brocquy at the Gorry Gallery, 20 Molesworth St, D2, from 28 June to 11 July