So, Prince William has finally decided that the time is right and he and Kate Middleton are to marry in 2011.

After eight years together, neither could be accused of rushing into it, and it seems likely that they have had time to discuss their expectations and wishes (as far as they are allowed to).

So why, oh why, on the day of the engagement itself, is Diana already the spectre at the feast?

OK, I'm not surprised that the media has evoked the ghost of Diana with the "Waity Katie"/Shy Di" comparisons, but William himself has placed her centre stage, by giving Kate his mother's distinctive sapphire ring. The ring forever associated with the girl who changed her mind, with unrequited love, eating disorders, and the public adulation mixed with private misery that characterised his mother's short life. Is it fair to ask Kate to start her married life with that legacy shining at her from her ring finger?

I am sure William loved his mother deeply and the fact that he appears to have coped so well with her tragic loss is testament to the quality of the relationship they obviously had. Yet he must understand that she cannot have a place in his marriage, Kate is a completely different person, and he must attend to her, in her own reality.

Therapists often see people who are unhappy in their relationships because their partners don't behave as they want them to. These ideas about acceptable behaviour are based on early experiences, the way they learnt that loved ones behave, in childhood. They take with them a template of expected behaviour, responses, and relational experience which gets applied to each new relationship. Pity their partner therefore who doesn't have this template, doesn't know the expectations, and undoubtedly has expectations of their own about the relationship! No wonder so many of us keep having that same old row, without understanding why.

What I'm trying to say is that these early experiences make it difficult to see who the other person really is, in their own entirety. William is as much prone to this as the rest of us, but by placing his mother's ring firmly on his fiancée's finger, it seems his expectations are clear. My worry for Kate Middleton is that she will find it hard to feel loved for who she is.

Johanna Sartori is a counsellor and psychotherapist working in Twickenham. Go to - www.johannasartori.co.uk