I went to the Ted Ellis Nature Reserve at Wheatfen in June 2005; I didn't see a Swallowtail butterfly so I photographed the noticeboard in the hide instead!
Research suggests that Swallowtail butterflies might be seen at the RSPB Nature Reserve called Strumpshaw Fen or the Bure Marshes National Nature Reserve with access at the Norfolk Wildlife Trust Centre at Ranworth Broad.
Size: 80mm or more (largest British butterfly - see list of butterflies by size)
First Generation flight period: May-July
Second Generation flight period: August-September in good years
Habitat: East Anglian Fens
Larval Food Plants: Milk Parsley (Peucedanum palustre), Angelica (Angelica sylvestris), Wild Carrot (Daucus carota), Fennel (Foeniculum vulgare)
Family Group: Papilionidae - see list of butterflies by family