This is 'Honesty' also known as 'Money Plant'.
Lunaria Annua. It's a biennial.

Thank you, Kassi. Now you've reminded me, I remember collecting the seeds from a friend's garden :)

These are so impressive when you grow a good large specimen! Remember to save seed from it and watch for next year's plants growing around it. It grows one year and flowers the next, then seeds and dies.

Thanks for the info, Volunteer, I have several of the plants in the garden so will watch out for seeds and self-seedlings :)