Stockbridge Marinated Venison

My friend Isabel Rutherford goes off every year to Skye. She stalks and, in her gum boots, climbs mountains that would challenge Sir Edmund Hilary. She returns with a battered ten-year-old stag, which even hounds might disdain, and serves it up chargrilled and tender as best fillet. I have wrung out of her the secret, although she is frightfully airy about this magic trick which even Escoffier might envy.