The Secret of the Flame Tree - S6-E2
Plot hole: For the murder to happen as described, the victim must have set an appointment at the cliff with a mentally ill, barely coherent person who spends her life holed up in a bungalow and is afraid of everyone, trusting her to remember and be on time - instead of knocking at her door and walk her to the location, that is very close. It's a complete absurdity.
Answer: Most likely they had only tropical exotic drinks, he wanted an old fashioned English beer.