Hello Lucy,
Its hard to see, but does the pupae have some smal silvery spots on the skin ?
Its not a swallowtail pupae, but I think it will be one of the Nymphalidae famely! But what kind of butterfly will come out, I dont can tell you, becourse the pupae do see simmelar of this famely, but the butteflies look different. Just wait and see what is comming out of it, and maybe take a picture so we can see what butterfly came out.
John.