pond plant I.D. please

Ive not bought this,must of been a stray mixed in from an aquatic buy but it popped up in 1 of my pond plant pots,its 1 stem and about 2ft tall
cheers julie x

 

Looks like Flowering Rush Butomus umbellatus

http://apps.rhs.org.uk/plantselector/plant?plantid=272

 

Thanks Aesculus i like pretty freebies i will put it in its own pot when it finishes flowering x

 

Yep it sure is; a lovely plant, I've grown it in the past. It also grows in the margins of our local canal round here....