unknown flower

Occasionally things get lost or forgotten about in the garden (probably a lot more that I realise), but this is very obvious this week as the above flower has started to bloom this week – and I have no idea what it is! I can’t remember planting it, and would love to know what it is if someone knows. The plant was there last year, but it didn’t flower, and the leaves have been there throughout the whole year (i.e. has never died off). I’ve checked all my seed packets and also searched online, but can’t find it. Let me know what you think ! Thank you 🙂