The letter, written in May 2010, six months before Anni was found shot dead in a taxi in South Africa, says she was "precious" to him but also reveals a rocky side to their relationship.
The pair were introduced through a mutual friend in May 2009, and were married 18 months later. But within days of their nuptials, Anni was dead and her widower was arrested on suspicion of her murder.
Dewani admitted in his first day in court to being bisexual and said he had rendezvous with male prostitutes, but denied arranging for his wife to be killed.
Western Cape High Court was told how their relationship was peppered with arguments and break-ups.
Graphic film showing Anni's body was shown to the court, drawing gasps from some of the audience and making Shrien bow his head.
Towards the end of May 2010, Anni and Dewani had a disagreement. The following letter, from the suspect to his wife, was read in court:
I think it is better if I write this rather than say it on the phone as then you can read it over and over ... I am really upset after out conversation. I realise we are very different but I have always believed in a relationship you can work through those differences. When we first met I immediately liked you ... And no not just because you are pretty ... but because you made me laugh. We had such a good time at the first dinner at Asia de Cuba.
I have always wanted a girl that I can be friends with. One that understands me - and I know that that is not easy. I know that I am so focussed that some people think I am intense. I am focussed on achieving things in life. I want to be someone who can do things - and that is not just about making money, but it is about having a rounded social life. A family, a business, an input into the community.
When we first met and started dating I knew that you were that girl. It does need to be right for both of us though.
I can't believe that I'm gonna write this, and I actually have tears in my eyes as I write it, but if you really think being with me is not going to make you happy then this is not right for you. I really hope that that is not what you are saying but I don't want to feel like I have forced you into something. I really do love you, and hence I don't want you to be unhappy. I want to be with you forever but not if that makes you unhappy ... that I could not bear ... I really hope we work this out.
I am really sorry that I have made you feel like this. You are so precious to me - I know I don't always show it. I often find it difficult to show how much you mean to me ... But please do not think this is because I don't love you.
Speak to you later