Thank you Marigold and Chris. She laid a normal egg yesterday morning, then c10pm I saw her straining and watched her lay an egg with no shell or skin and only part of the skin. Over half of it is still inside her, but nothing is protruding. Today she was sitting quietly in a corner, so is now relaxing in a cat box so I can monitor her. I've tried some lubrication and steaming. She was perhaps upset yesterday as a hen had gone broody where she normally lays. I'll try applying a bit of tension. I'm not sure how well a vet would deal with this if she can't expel it naturally?