Mystery Plant

Any ideas what this fruiting weed might be? I suspect it's a physalis or Cape Gooseberry.

Unfortunately, as observant readers will have noticed, it's a bit late for identification. The plant was already in the skip by the time I realised that there was fruit on it. I found it in the front border, growing underneath an aloe. I'm not sure how it got there - maybe one of the builders had an exotic taste in snacks...