Hi Charlie yes cut the flowering stem out completely and the lupin should flower again. Will die back completely to the ground in late autumn and then grow again in spring.

Thanks Moon grower, that's really helpful
- while we're on the subject, what about Oriental Poppies? I'm leaving the seed heads un-cut as I think it's almost at the end of its flowering, only a couple more un-opened buds. Instinct tells me not to cut the seed heads off, but my instinct could be way off!
Thanks again
Charlie

Oriental poppies are on of the few perennials that don't set more flowers if you deadhead them. I'd leave the seed heads on as they look spectacular for months, when they start to look dry and like a pepper pot carefully remove the seed head, keeping it upright, and place in a paper bag. Leave to dry off completely and shake out the seed into the bag... you can then grow more poppies from seed next spring. Alternatively let the poppies seed themselves but you then have to make sure you don't weed them out!

Thanks Moon grower, I'm impressed by your knowledge and expertise. I also have annual poppies from scattered seeds saved from previous years, so it's the same process, except the Orientals are perennial...?
Thank you for all your help
Charlie