Gently take hold of the stalk at the base of the leaf that the flower came out of. With the other hand, take hold of the dead flower at the base of the petals, being careful not to pinch the neighboring flower bud. Gently twist and pull the dead flower out, hopefully taking out the developing seed pod underneath. Taking the seeds out will help the plant bloom more next spring--or sooner, if it's a re-bloomer.
If you are breeding new varieties and want to save the seeds, simply snip the petals off with vegetable shears, about 7 mm above the base of the petals.

How does one work with the seeds? How long does it take to produce an iris from seed? I have one (see latest photos) which I would like to try getting seeds from though I realise I can also multiply by cutting the rhizomes in due course.

Keep an eye on the pods, Cestina, and don't pick them until they are starting to turn brownish, and maybe splitting a bit. Once they're ready, pick them and put them in a paper bag to dry and open for about a week. Plant the seeds right away in a garden bed or seed pan, about 1/2 cm deep, and moisten them twice a day until they sprout--about 3 weeks. New seedlings look like onion seedlings, only more strap shaped. They should develop a few more leaves before winter, and should be left out through the winter, though with shelter, if started in a pot. Early next spring, set out the ones that were in a pot, and feed all of them with a balanced fertilizer. Feed again in late July, to acommodate the fall growth spurt. You may get some blooms in 2012, but some of the best ones will wait until 2013 to bloom. Since modern bearded Iris are complex hybrids, probably all of the offspring are likely to be different from Mama and each other, most of them even better adapted to your climate than their parents were. Good luck in that, Cestina!

Many thanks Tugbrethil....I shall try.......and meanwhile there are always the rhizomes :-)

Thank goodness for them!