Sandy Nairne: They don't begin and end with Kylie Minogue and Judy Garland

This year is the 40th anniversary of the Stonewall riots in New York – a marker for many in the gay community in terms of resistance and overcoming the negative attitudes and discrimination that gay people have experienced for so long. But what we wanted to say with this exhibition is that while it is an important anniversary, it is a very good moment to celebrate the diversity of the achievements of gay people over these years. The way in which we wanted to stage the exhibition was not simply to follow a set-piece idea of what other people might think were the "classic" gay icons, but instead to invite a number of distinguished figures, from many different backgrounds and places, to become our selectors and to ask "Who is it that is iconic for you?" The selectors have interpreted what "iconic" means in very different ways. But centrally there is a strong sense of inspiration. Of course, there is a crossover with the broader themes of equality, tackling discrimination and finding ways to overcome it.

I think it would have been quite wrong to limit the icons to those who are themselves gay. I admit there is a certain ambiguity in the exhibition's title, but I think this is a very creative ambiguity which opens up questions about what being gay means and also questions what "iconic" might mean.

The gallery has got nothing against the classic Judy Garland and Kylie Minogue figures – such images appear in the book we are publishing with the show, where Richard Dyer examines the stereotypes within the terminology of gay icons. But for the exhibition itself we wanted to focus on those who were inspirational for the selectors. The fact that the selectors are themselves gay doesn't mean they only identify with other gay figures.

I raised the idea for the show with the gallery's trustees two years ago. Everyone felt it was consistent with our exhibitions programme. If it is bold, I hope it is bold in a fascinating and exciting way and that it will draw visitors into the stories told through the portraits. There are such good stories to tell, and many more will be revealed nearer the July opening.

Sandy Nairne is the director of the National Portrait Gallery