I was given some good advice by my elder daughter over the weekend when we were talking about the Taylor Wessing Portrait competition run by the NPG. She said that one way to distinguish between the impact of possible portraits I might enter is to choose the one which hints at a narrative, or tempts the viewer to create a story because the expression is so strong, or which has a quizzical quality that appears to suggest there is a story to be found behind the eyes.

What is always certain is that it must be technically exceptional (unless it is deliberately using a technique that makes a premeditated virtue of a lack of sharp focus, or even composition. Last year's winning entry was a very sharp group portrait of the photographer's daughter and four of her friends, some of their possessions on the table in front of them. Not one of the five girls caught the eye of the camera. So it looked deliberately staged, stylised. Although supposedly friends, they looked detached from one another, almost as if the word 'friend' was being defined as a Facebook construct where friendship has been confused with mere casual contact, and thus been devalued.

Maybe that's what the photographer was saying; that today it is difficult for young people to know not only who one's real friends are, but also what that friendship stands for. In that sense, it made me think. It wasn't the image I would have chosen to win but it made me think. It started a conversation inside me.

Do I have a portrait that does the same thing? I will be showing the five or six portraits I have shortlisted to others - some knowledgeable about photography, others because they will give me an honest, 'layman's' response. Hopefully, out of that process, it will be easier, rather than more difficult, to make my choice.

One good omen: the NPG sent me an email today to remind me of the closing date for entries (July 5th).