Thanks everybody,
I'm not that much of an expert, the lighting set-up is an easy classic : Soft light from the front to one side, hard light from the back to the other side. For a sweet and flattering portrait, point the face towards the soft light. In the sixties and seventies, you could find hundreds of these in the shop-windows of photographers.
Point the side of the head to the soft light for a more sculptural effect : the front of the face is in shadow, the wrinkles become more apparent. In the 70ties and 80ties, you could find diagrams for something like this in all the photo-magazines, with learnéd expositions about ratios of light and candle feet.
And the pose is an old stand-by too. I think it was invented by a painter doing a self-portrait : the painter is sitting square to his canvas, an then looks to his side at the mirror. The shape of the head is shown front and side, the shoulders at an angle flatter the torso, and the eyes looking from the side make for an interesting look.
It is amazing, how just following the rules can get you so much satisfaction. Nothing 'new', nothing 'creative', but still a very effective way to organise a portrait.
Now I'm dreaming of doing 'royal' portraits of my friends. Sitting or standing full figure, with 'attributes' and a curtain acting floppy behind them.
Here's a picture of my mum, she's a painter :
Cheers