@Magdlyn - We are heading for couples counselling. Actually we are communicating better now than ever before. If we had had this level of communication earlier, and I'd felt able to discuss polyamory with T before embarking on the affair I wonder if things might have been different. I'm not sure they would though. As for hypocrisy. Yes it does sound like "one rule for me, one rule for you". I had hoped that T would be able to come to terms with Polyamory because of her own experience. But it was not to be.
@MonoVPCHG. Thanks for the supportive words. Means a lot. Along with other responses yours encourages me to not feel sorry for myself, which is good. As to whether or not I'd consider another polyamorous situation - at the moment no. I didn't set out to be polyamorous, it was something I discovered about myself by falling in love again. I can't see me falling in love again so I don't think it's going to arise. However if it did happen I hope that T and I would be able to talk first before I acted.
Can I say how much all these responses have helped me? You are wonderful people. Thanks.