A Zed & Two Noughts (1986)

Oliver Deuce, a successful doctor, is shattered when his wife is killed in a freak car accident involving the car being driven by Alba Bewick colliding with a very large rare bird. His twin brother Oswald is researching how carcasses decay at the local zoo. Alba survives the accident although she loses one leg, and her sinister physician eventually removes the other 'because it looked so sad all alone'. Oswald and Oliver become involved in a menage a trois with Alba, and uncover very dubious trafficking in zoo property. But ultimately their only goal is to try and understand their mortal condition.