Spotted this fantastic example in the car park at work, next to a rail line. Measuring approx 4" long with 5" wingspan.
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Just note that the spelling for Emperor Dragonfly is Anax imperator and that the species name does not require a capital letter.
Whether that is the correct ID is one for someone else!
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Lat/Lng: 51.3415, -2.9731
OS grid ref: ST323607