wild Gladiolus? No.

When we asked we were told this beautiful plant was a "wild Gladiolus". Perhaps they have naturalized in Sissinghurst, which is where this photo was taken. Web searches on "wild Gladiolus" don't immediately come back with an unambiguous identity, so I emailed Sissinghurst, who, everhelpful, corrected us.

Hi Brent,

The plant you saw was Dierama pulcherrimum, Hopefully, when you google it now, you will be able to see it. It’s a lovely plant and easy to grow too.

Kind regards,

Helen Champion

What a rewarding email to read.  Indeed, Helen has it exactly right.  It's also known as a Fairy Wand or Wand Plant according to Native Sons Nursery who seem to occasionally stock it.

See also Pacific Bulb Society.

It turns out to be a hard plant to find in my area.  I have ordered one bare root plant and 20 seeds from out of state.  We'll see how it goes.