In the BBC documentary "Yes, Minister - A View from Whitehall" (2011), Lord Bernard Donoughue stated that a similar situation with the liquor actually took place in 1978 on a visit to Pakistan with Prime Minister James Callaghan. Donoughue was included in the group for that visit, and he devised and carried out the scheme himself without the knowledge of the PM, who didn't drink. Donoughue was one of the writers' advisers and had secretly informed them of this.
In real life, Qumran is an archaeological site in Israel, near the Dead Sea. It is the place where the Dead Sea Scrolls were first discovered during the 1940's. Apart from the name, it has no connection to this episode's subject.