On the banks of the Ouseburn in Jesmond Dene, near the Eye Bridge.
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does look rather like Leucojum but probably not native there?
Agreed. The Dene was bought by Lord Armstrong who would have done a lot of planting and he then gave it to the city. Since then the Park Keepers will have planted stuff as well but I've also seen members of the public planting flowers! There's no telling what occurs naturally and what's been introduced.
I've been back and it's definitely aestivum, 3 to 5 flowers per umbel, tepal length 20 to 25 mm. There seemed to be the occasional tooth on the corners of the stem which implies ssp aestivum rather than ssp pulchellum, which I was expecting!
Lat/Lng: 55.0, -1.7
OS grid ref: NZ2567