Late in the summer of 1865, the French and British navies exchanged formal visits, with a British fleet visit to Cherbourg followed by a reciprocal French visit to Portsmouth. In the latter town, two balls were held, both documented in engravings and written coverage by, among others, the Illustrated London News. The image at left (click to enlarge) illustrates the ball held on Thursday, August 31st, 1865, in a "grand pavilion erected for the entertainments on Governor’s Green." ("Illustrations of the Naval Festival at Portsmouth." Illustrated London News (London, England), Issue 1333, Saturday, September 9, 1865). More detailed coverage a week later explained that the ball was held in
one of Edgington’s tents, 138 ft. long and 36 ft. wide, floored over, and lined with crimson and white cloth, also decorated with flags and coloured lamps. At the upper end, behind the Mayor’s chair, was a bust of the Emperor Napoleon, above a shield bearing the arms of the town of Portsmouth, with the Mayor’s chain and badge. On his right hand were the Royal arms of Great Britain, supported by the standards of France, with the Imperial and British crowns. On his left hand were the arms of France, supported by the Royal standards of England and of the Prince of Wales. At the opposite end of the room were an exquisitely-designed waterfall, fountain, and cascade, intermixed with choice ferns and evergreens — the rockwork before formed of blocks of coal, gilt...The company numbered about 2000 ladies and gentlemen, and the great majority of the latter wore naval or military uniforms, while the ladies, of course, were very richly and gaily dressed. They presented, while dancing, a splendid as well as a lively and animated sight.
-- "Illustrations of the Anglo-French Naval Festival at Portsmouth." Illustrated London News (London, England), Issue 1334, Saturday, September 16, 1865.