More elaborately: the killer took time to create a series of circles on the victim's lawn, and cold-clocks him when he goes out to investigate. The killer ties him down in the middle by hammering croquet hoops over him.
Inside, the killer approaches the wife - wheelchair bound, instead of hurting her, he just wheels her to a window overlooking the lawn, and locks her wheel so she can't phone the police.
Then he takes the victim's mini catapult (the man's an expert on Roman Britain), and starts to hurl the man's wine bottles at him. At first the victim freaks out about his expensive rare wines being tossed.