Macrophya montana
At least two vernacular names have been proposed for this species: Yellow-spotted Macrophya and Dimorphic Strider.
I suspect that with a bit of experience this species will be immediately recognisable in the field, let alone needing to be keyed out carefully as I did with this. The hind femora weren't obviously longer than the abdomen but the labrum was convex which helps separate this genus from Tenthredo, some of which are fairly similar.
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Macrophya montana showing labrum, Tivetshall St Margaret's (Norfolk, UK), 10th June 2023
Macrophya montana, North Elmham Cathedral Meadows (Norfolk, UK), 21st June 2019
This one evaded capture so is identified solely from these photos.
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Macrophya montana, Wendling Beck Environment Project (Norfolk, UK), 7th June 2024
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male & female Macrophya montana, Wendling Beck Environment Project (Norfolk, UK), 13th June 2024