From Ruth Tongue's Forgotten Folk-tales of the English Counties, told by Harry White in Middlesex in 1936.
here were two labourers crossing Stanmore Common when the grigs were playing in the bracken. Two of them put on their red caps and vanished but the third was in such a panic that he pulled the red cap too hard and fell into it like a sack. Then all he could do was keep still till the men passed on, but one of them saw the red hat.
"Here's luck," said he. "A nice, large, red cap."
"Leave it lay," says t'other man.
"Not me--I'm needing a smart hat myself."
"Leave it lay," says his mate, very worried.
But no, not he. He puts it on right over his ears and if the grig was unhappy before, now he couldn't breathe. He began to kick and twist and pull his hair and thump, and so did the labourer only he game himself the beating.
His mate watched him while he yelled, "There's the father and mother of all hornets inside it, and don't I know it!"
And somehow he dragged it off.
The red cap was out of his reach in a second and something shot out of it and was gone with it crying, "You was told to leave it lay."
Then all the bracken rang with grig laughter and the men ran like hell.