Could be an iris?

Possibly the wild bog Iris pseudacorus with the yellow flower in early summer. But its really difficult to ID from this picture as so many plants have long strappy leaves.

Thank you both.

Don't think that it ia an iris by the way the centre pair of leaves have come from one base (I don't know how to say what I mean but see those central leaves at the bottom of the picture). I would suggest it may be Montbretia.

Well... ust admit Bulbaholic..my first thought was montbretia, but the contributor says it was growing in amongst a clump of montbretia. Still...could be a taller variety. To my eye, the leaves dont look strong enough for Iris.

I was thinking one of the larger Gladiolus varieties, but how that would suddenly appear in a clump of Montbretia is beyond me. If the clump was recently planted, it might have been accidentally mixed in with the Montbretia bulbs at the garden center.

Thank you for your answers.This clump of montbretia has been in this spot for years but this one has only appeared this year.It dosn't look like montbretia so will wait and see if any flowers appear.

If it is a Gladiolus started from seed, it would have blended in with the Montbretia for the last two years. It's hard to tell if it will bloom this year, but it's certainly big enough.

It looks like a crocosmia to me and the only one I have that tall is 'Lucifer'. Maybe a "rogue" bulb in with the smaller ones.