Given the task definition and input, reply with output. This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

Britain was concerned about Russian activity and Sir John Burgoyne senior advisor to Lord Aberdeen urged that the Dardanelles should be occupied and throw up works of sufficient strength to block any Russian move to capture Constantinople and gain access to the Mediterranean Sea. The Corps of Royal Engineers sent men to the Dardanelles while Burgoyne went to Paris, meeting the British Ambassador and the French Emperor. The Lord Cowley wrote on 8 February to Burgoyne "Your visit to Paris has produced a visible change in the Emperor's views, and he is making every preparation for a land expedition in case the last attempt at negotiation should break down.":411
Who was concerned with Russia  capturing Constantinople?