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There is usually a small convex part of the gall above the leaf as well as the larger part below. Think that can just be seen in the first photo.
Currant galls also appear on male catkins.
Different generation of same species causes common spangle galls in late summer.
Many thanks for your comments - very informative and much appreciated.
Lat/Lng: 51.7294, -2.0963
OS grid ref: SO934034