Large flying beetles

Observation - Large flying beetles - UK and Ireland. Description: large (similar size to stag beetle) black, flying beetles seen singly during evenings through August and early September. Long feathery antennae(?) like Maybugs but longer. Poor doddery flight, eventually rising. One sighting during day

large (similar size to stag beetle) black, flying beetles seen singly during evenings through August and early September.
Long feathery antennae(?) like Maybugs but longer.
Poor "doddery" flight, eventually rising.
One sighting during day