I have been to the vet tonight with Em - and we no longer have Nat. Julie our vet was amazed at how old she was - getting to 3 is a rare achievement for a rat. Looks like she had either pneumonia or a tumour in her lungs and Em made the decision for euthanasia. She wasn't going to stay in the room as she was so upset but decided to stay with me and hold Nat as she was sedated. She is so good when it comes to her animals - and Nat's welfare was more important than hers at that time. I am very proud of her.