The Comfort of Strangers

Question: I have two questions about Robert and Caroline. First, why are there two separate beds in their bedroom? I know that Colin and Mary's hotel room might have had two single beds by default, but was it common practice for Italian homes to still contain separate beds in the 1990s? Also, why did Robert and Caroline murder Colin?

Chosen answer: While it's possible that they slept in separate beds because of Caroline's chronic back pain, and Robert could accidentally hurt her in the night by moving, it's more likely that it's a sexual kink of sorts, a way to 'deprive' them both of each other. They murdered Colin because Robert was highly unstable (Caroline was utterly dependent on him and was also unstable as a result) and since they enjoyed pain during sex, it's implied that they thought it would be a great sexual thrill to seriously hurt someone else, which would explain why they appeared amorous with each other as soon as Robert cut Colin's throat.