His absence has put noses out of joint in the Austrian presidency of the EU, because Mr Cook has the most recent experience of chairing the "general affairs council" of foreign ministers, during the six months of the British presidency that ended in July. As outgoing chairman, Britain is a member of the so-called "troika", made up of the current, the present and the next presidencies.
The informal foreign ministers' meetings are designed to allow them to brainstorm in a relaxed, private setting, generally a restored castle, chateau or country residence. Mr Cook's new wife, Gaynor, would have been invited.
One Brussels-based diplomat said: "This is very surprising, given that the particular subject matter is ways of making foreign ministers more relevant. Perhaps one way of doing that would be to turn up to meetings."
Mr Cook's place will be taken by Joyce Quin, Minister of State for Europe. Although she is respected for her knowledge of European affairs, she has little experience of the general affairs council because she took over her post only in the summer reshuffle, after Britain's presidency ended.
Mr Cook's absence is all the more surprising since he contributed a paper to today's discussion. An Austrian government spokesman said: "He is not going to attend and we will certainly miss him. We are going to discuss his very interesting paper."
In private, Austrian officials admitted to disappointment at Mr Cook's refusal to break his holiday, adding that the paper "was supposed to be discussed in his presence".
The Foreign Office said that Mr Cook had worked throughout August on the understanding he would take his holiday in September.Reuse content